Merge branch 'master' into es-modules-work

30 files changed, 477 insertions, 336 deletions

diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index 9a827546f..d5df17020 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -3546,10 +3546,10 @@ ComputeDrawnSizeForBackground(const CSSSizeOrRatio& aIntrinsicSize,
     imageSize.width = ComputeRoundedSize(imageSize.width, aBgPositioningArea.width);
     if (!isRepeatRoundInBothDimensions &&
         aLayerSize.mHeightType == nsStyleImageLayers::Size::DimensionType::eAuto) {
-      // Restore intrinsic rato
-      if (aIntrinsicSize.mRatio.width) {
-        float scale = float(aIntrinsicSize.mRatio.height) / aIntrinsicSize.mRatio.width;
-        imageSize.height = NSCoordSaturatingNonnegativeMultiply(imageSize.width, scale);
+      // Restore intrinsic ratio
+      if (aIntrinsicSize.mRatio) {
+        imageSize.height =
+            aIntrinsicSize.mRatio.Inverted().ApplyTo(imageSize.width);
       }
     }
   }
@@ -3560,10 +3560,9 @@ ComputeDrawnSizeForBackground(const CSSSizeOrRatio& aIntrinsicSize,
     imageSize.height = ComputeRoundedSize(imageSize.height, aBgPositioningArea.height);
     if (!isRepeatRoundInBothDimensions &&
         aLayerSize.mWidthType == nsStyleImageLayers::Size::DimensionType::eAuto) {
-      // Restore intrinsic rato
-      if (aIntrinsicSize.mRatio.height) {
-        float scale = float(aIntrinsicSize.mRatio.width) / aIntrinsicSize.mRatio.height;
-        imageSize.width = NSCoordSaturatingNonnegativeMultiply(imageSize.height, scale);
+      // Restore intrinsic ratio
+      if (aIntrinsicSize.mRatio) {
+        imageSize.width = aIntrinsicSize.mRatio.ApplyTo(imageSize.height);
       }
     }
   }
@@ -5264,17 +5263,11 @@ CSSSizeOrRatio::ComputeConcreteSize() const
     return nsSize(mWidth, mHeight);
   }
   if (mHasWidth) {
-    nscoord height = NSCoordSaturatingNonnegativeMultiply(
-      mWidth,
-      double(mRatio.height) / mRatio.width);
-    return nsSize(mWidth, height);
+    return nsSize(mWidth, mRatio.Inverted().ApplyTo(mWidth));
   }
 
   MOZ_ASSERT(mHasHeight);
-  nscoord width = NSCoordSaturatingNonnegativeMultiply(
-    mHeight,
-    double(mRatio.width) / mRatio.height);
-  return nsSize(width, mHeight);
+  return nsSize(mRatio.ApplyTo(mHeight), mHeight);
 }
 
 CSSSizeOrRatio
@@ -5297,6 +5290,16 @@ nsImageRenderer::ComputeIntrinsicSize()
       if (haveHeight) {
         result.SetHeight(nsPresContext::CSSPixelsToAppUnits(imageIntSize.height));
       }
+
+      if (!haveHeight && haveWidth && result.mRatio) {
+        nscoord intrinsicHeight =
+            result.mRatio.Inverted().ApplyTo(imageIntSize.width);
+        result.SetHeight(nsPresContext::CSSPixelsToAppUnits(intrinsicHeight));
+      } else if (haveHeight && !haveWidth && result.mRatio) {
+        nscoord intrinsicWidth = result.mRatio.ApplyTo(imageIntSize.height);
+        result.SetWidth(nsPresContext::CSSPixelsToAppUnits(intrinsicWidth));
+      }
+
       break;
     }
     case eStyleImageType_Element:
@@ -5379,9 +5382,7 @@ nsImageRenderer::ComputeConcreteSize(const CSSSizeOrRatio& aSpecifiedSize,
   if (aSpecifiedSize.mHasWidth) {
     nscoord height;
     if (aIntrinsicSize.HasRatio()) {
-      height = NSCoordSaturatingNonnegativeMultiply(
-        aSpecifiedSize.mWidth,
-        double(aIntrinsicSize.mRatio.height) / aIntrinsicSize.mRatio.width);
+      height = aIntrinsicSize.mRatio.Inverted().ApplyTo(aSpecifiedSize.mWidth);
     } else if (aIntrinsicSize.mHasHeight) {
       height = aIntrinsicSize.mHeight;
     } else {
@@ -5393,9 +5394,7 @@ nsImageRenderer::ComputeConcreteSize(const CSSSizeOrRatio& aSpecifiedSize,
   MOZ_ASSERT(aSpecifiedSize.mHasHeight);
   nscoord width;
   if (aIntrinsicSize.HasRatio()) {
-    width = NSCoordSaturatingNonnegativeMultiply(
-      aSpecifiedSize.mHeight,
-      double(aIntrinsicSize.mRatio.width) / aIntrinsicSize.mRatio.height);
+    width = aIntrinsicSize.mRatio.ApplyTo(aSpecifiedSize.mHeight);
   } else if (aIntrinsicSize.mHasWidth) {
     width = aIntrinsicSize.mWidth;
   } else {
@@ -5406,32 +5405,57 @@ nsImageRenderer::ComputeConcreteSize(const CSSSizeOrRatio& aSpecifiedSize,
 
 /* static */ nsSize
 nsImageRenderer::ComputeConstrainedSize(const nsSize& aConstrainingSize,
-                                        const nsSize& aIntrinsicRatio,
+                                        const AspectRatio& aIntrinsicRatio,
                                         FitType aFitType)
 {
-  if (aIntrinsicRatio.width <= 0 && aIntrinsicRatio.height <= 0) {
+  if (!aIntrinsicRatio) {
     return aConstrainingSize;
   }
 
-  float scaleX = double(aConstrainingSize.width) / aIntrinsicRatio.width;
-  float scaleY = double(aConstrainingSize.height) / aIntrinsicRatio.height;
+  // Suppose we're doing a "contain" fit. If the image's aspect ratio has a
+  // "fatter" shape than the constraint area, then we need to use the
+  // constraint area's full width, and we need to use the aspect ratio to
+  // produce a height. ON the other hand, if the aspect ratio is "skinnier", we
+  // use the constraint area's full height, and we use the aspect ratio to
+  // produce a width. (If instead we're doing a "cover" fit, then it can easily
+  // be seen that we should do precisely the opposite.)
+  //
+  // This is equivalent to the more descriptive alternative:
+  //
+  //   AspectRatio::FromSize(aConstrainingSize) < aIntrinsicRatio
+  //
+  // But gracefully handling the case where one of the two dimensions from
+  // aConstrainingSize is zero. This is easy to prove since:
+  //
+  //   aConstrainingSize.width / aConstrainingSize.height < aIntrinsicRatio
+  //
+  // Is trivially equivalent to:
+  //
+  //   aIntrinsicRatio.width < aIntrinsicRatio * aConstrainingSize.height
+  //
+  // For the cases where height is not zero.
+  //
+  // We use float math here to avoid losing precision for very lareg backgrounds
+  // since we use saturating nscoord math otherwise.
+  const float constraintWidth = float(aConstrainingSize.width);
+  const float hypotheticalWidth =
+      aIntrinsicRatio.ApplyToFloat(aConstrainingSize.height);
+
   nsSize size;
-  if ((aFitType == CONTAIN) == (scaleX < scaleY)) {
+  if ((aFitType == CONTAIN) == (constraintWidth < hypotheticalWidth)) {
     size.width = aConstrainingSize.width;
-    size.height = NSCoordSaturatingNonnegativeMultiply(
-                    aIntrinsicRatio.height, scaleX);
+    size.height = aIntrinsicRatio.Inverted().ApplyTo(aConstrainingSize.width);
     // If we're reducing the size by less than one css pixel, then just use the
     // constraining size.
     if (aFitType == CONTAIN && aConstrainingSize.height - size.height < nsPresContext::AppUnitsPerCSSPixel()) {
       size.height = aConstrainingSize.height;
     }
   } else {
-    size.width = NSCoordSaturatingNonnegativeMultiply(
-                   aIntrinsicRatio.width, scaleY);
+    size.height = aConstrainingSize.height;
+    size.width = aIntrinsicRatio.ApplyTo(aConstrainingSize.height);
     if (aFitType == CONTAIN && aConstrainingSize.width - size.width < nsPresContext::AppUnitsPerCSSPixel()) {
       size.width = aConstrainingSize.width;
     }
-    size.height = aConstrainingSize.height;
   }
   return size;
 }
diff --git a/layout/base/nsCSSRendering.h b/layout/base/nsCSSRendering.h
index 791e9656e..8ebeb7537 100644
--- a/layout/base/nsCSSRendering.h
+++ b/layout/base/nsCSSRendering.h
@@ -17,6 +17,7 @@
 #include "nsLayoutUtils.h"
 #include "nsStyleStruct.h"
 #include "nsIFrame.h"
+#include "mozilla/AspectRatio.h"
 
 class gfxDrawable;
 class nsStyleContext;
@@ -41,8 +42,7 @@ class ImageContainer;
 struct CSSSizeOrRatio
 {
   CSSSizeOrRatio()
-    : mRatio(0, 0)
-    , mHasWidth(false)
+    : mHasWidth(false)
     , mHasHeight(false) {}
 
   bool CanComputeConcreteSize() const
@@ -50,12 +50,12 @@ struct CSSSizeOrRatio
     return mHasWidth + mHasHeight + HasRatio() >= 2;
   }
   bool IsConcrete() const { return mHasWidth && mHasHeight; }
-  bool HasRatio() const { return mRatio.width > 0 && mRatio.height > 0; }
+  bool HasRatio() const { return !!mRatio; }
   bool IsEmpty() const
   {
     return (mHasWidth && mWidth <= 0) ||
            (mHasHeight && mHeight <= 0) ||
-           mRatio.width <= 0 || mRatio.height <= 0; 
+           !mRatio; 
   }
 
   // CanComputeConcreteSize must return true when ComputeConcreteSize is
@@ -67,7 +67,7 @@ struct CSSSizeOrRatio
     mWidth = aWidth;
     mHasWidth = true;
     if (mHasHeight) {
-      mRatio = nsSize(mWidth, mHeight);
+      mRatio = AspectRatio::FromSize(mWidth, mHeight);
     }
   }
   void SetHeight(nscoord aHeight)
@@ -75,7 +75,7 @@ struct CSSSizeOrRatio
     mHeight = aHeight;
     mHasHeight = true;
     if (mHasWidth) {
-      mRatio = nsSize(mWidth, mHeight);
+      mRatio = AspectRatio::FromSize(mWidth, mHeight);
     }
   }
   void SetSize(const nsSize& aSize)
@@ -84,16 +84,16 @@ struct CSSSizeOrRatio
     mHeight = aSize.height;
     mHasWidth = true;
     mHasHeight = true;
-    mRatio = aSize;    
+    mRatio = AspectRatio::FromSize(mWidth, mHeight);    
   }
-  void SetRatio(const nsSize& aRatio)
+  void SetRatio(const AspectRatio& aRatio)
   {
     MOZ_ASSERT(!mHasWidth || !mHasHeight,
                "Probably shouldn't be setting a ratio if we have a concrete size");
     mRatio = aRatio;
   }
 
-  nsSize mRatio;
+  AspectRatio mRatio;
   nscoord mWidth;
   nscoord mHeight;
   bool mHasWidth;
@@ -184,11 +184,9 @@ public:
   /**
    * Compute the size of the rendered image using either the 'cover' or
    * 'contain' constraints (aFitType).
-   * aIntrinsicRatio may be an invalid ratio, that is one or both of its
-   * dimensions can be less than or equal to zero.
    */
   static nsSize ComputeConstrainedSize(const nsSize& aConstrainingSize,
-                                       const nsSize& aIntrinsicRatio,
+                                       const mozilla::AspectRatio& aIntrinsicRatio,
                                        FitType aFitType);
   /**
    * Compute the size of the rendered image (the concrete size) where no cover/
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index fdcdcac78..74dbd63e6 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -3966,7 +3966,7 @@ nsLayoutUtils::GetTextShadowRectsUnion(const nsRect& aTextAndDecorationsRect,
 enum ObjectDimensionType { eWidth, eHeight };
 static nscoord
 ComputeMissingDimension(const nsSize& aDefaultObjectSize,
-                        const nsSize& aIntrinsicRatio,
+                        const AspectRatio& aIntrinsicRatio,
                         const Maybe<nscoord>& aSpecifiedWidth,
                         const Maybe<nscoord>& aSpecifiedHeight,
                         ObjectDimensionType aDimensionToCompute)
@@ -3977,21 +3977,15 @@ ComputeMissingDimension(const nsSize& aDefaultObjectSize,
   // 1. "If the object has an intrinsic aspect ratio, the missing dimension of
   //     the concrete object size is calculated using the intrinsic aspect
   //     ratio and the present dimension."
-  if (aIntrinsicRatio.width > 0 && aIntrinsicRatio.height > 0) {
+  if (aIntrinsicRatio) {
     // Fill in the missing dimension using the intrinsic aspect ratio.
-    nscoord knownDimensionSize;
-    float ratio;
     if (aDimensionToCompute == eWidth) {
-      knownDimensionSize = *aSpecifiedHeight;
-      ratio = aIntrinsicRatio.width / aIntrinsicRatio.height;
-    } else {
-      knownDimensionSize = *aSpecifiedWidth;
-      ratio = aIntrinsicRatio.height / aIntrinsicRatio.width;
+      return aIntrinsicRatio.ApplyTo(*aSpecifiedHeight);
     }
-    return NSCoordSaturatingNonnegativeMultiply(knownDimensionSize, ratio);
+    return aIntrinsicRatio.Inverted().ApplyTo(*aSpecifiedWidth);
   }
 
-  // 2. "Otherwise, if the missing dimension is present in the object’s
+  // 2. "Otherwise, if the missing dimension is present in the object's
   //     intrinsic dimensions, [...]"
   // NOTE: *Skipping* this case, because we already know it's not true -- we're
   // in this function because the missing dimension is *not* present in
@@ -4029,7 +4023,7 @@ ComputeMissingDimension(const nsSize& aDefaultObjectSize,
 static Maybe<nsSize>
 MaybeComputeObjectFitNoneSize(const nsSize& aDefaultObjectSize,
                               const IntrinsicSize& aIntrinsicSize,
-                              const nsSize& aIntrinsicRatio)
+                              const AspectRatio& aIntrinsicRatio)
 {
   // "If the object has an intrinsic height or width, its size is resolved as
   // if its intrinsic dimensions were given as the specified size."
@@ -4076,15 +4070,13 @@ MaybeComputeObjectFitNoneSize(const nsSize& aDefaultObjectSize,
 static nsSize
 ComputeConcreteObjectSize(const nsSize& aConstraintSize,
                           const IntrinsicSize& aIntrinsicSize,
-                          const nsSize& aIntrinsicRatio,
+                          const AspectRatio& aIntrinsicRatio,
                           uint8_t aObjectFit)
 {
   // Handle default behavior (filling the container) w/ fast early return.
   // (Also: if there's no valid intrinsic ratio, then we have the "fill"
   // behavior & just use the constraint size.)
-  if (MOZ_LIKELY(aObjectFit == NS_STYLE_OBJECT_FIT_FILL) ||
-      aIntrinsicRatio.width == 0 ||
-      aIntrinsicRatio.height == 0) {
+  if (MOZ_LIKELY(aObjectFit == NS_STYLE_OBJECT_FIT_FILL) || !aIntrinsicRatio) {
     return aConstraintSize;
   }
 
@@ -4171,7 +4163,7 @@ HasInitialObjectFitAndPosition(const nsStylePosition* aStylePos)
 /* static */ nsRect
 nsLayoutUtils::ComputeObjectDestRect(const nsRect& aConstraintRect,
                                      const IntrinsicSize& aIntrinsicSize,
-                                     const nsSize& aIntrinsicRatio,
+                                     const AspectRatio& aIntrinsicRatio,
                                      const nsStylePosition* aStylePos,
                                      nsPoint* aAnchorPoint)
 {
@@ -5092,10 +5084,12 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis              aAxis,
            styleMinBSize.GetCoordValue() == 0)) ||
         styleMaxBSize.GetUnit() != eStyleUnit_None) {
 
-      nsSize ratio(aFrame->GetIntrinsicRatio());
-      nscoord ratioISize = (horizontalAxis ? ratio.width  : ratio.height);
-      nscoord ratioBSize = (horizontalAxis ? ratio.height : ratio.width);
-      if (ratioBSize != 0) {
+      AspectRatio ratio = aFrame->GetIntrinsicRatio();
+      if (ratio) {
+        // Convert 'ratio' if necessary, so that it's storing ISize/BSize:
+        if (!horizontalAxis) {
+          ratio = ratio.Inverted();
+        }
         AddStateBitToAncestors(aFrame,
             NS_FRAME_DESCENDANT_INTRINSIC_ISIZE_DEPENDS_ON_BSIZE);
 
@@ -5111,14 +5105,14 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis              aAxis,
             (aPercentageBasis.isNothing() &&
              GetPercentBSize(styleBSize, aFrame, horizontalAxis, h))) {
           h = std::max(0, h - bSizeTakenByBoxSizing);
-          result = NSCoordMulDiv(h, ratioISize, ratioBSize);
+          result = ratio.ApplyTo(h);
         }
 
         if (GetDefiniteSize(styleMaxBSize, aFrame, !isInlineAxis, aPercentageBasis, &h) ||
             (aPercentageBasis.isNothing() &&
              GetPercentBSize(styleMaxBSize, aFrame, horizontalAxis, h))) {
           h = std::max(0, h - bSizeTakenByBoxSizing);
-          nscoord maxISize = NSCoordMulDiv(h, ratioISize, ratioBSize);
+          nscoord maxISize = ratio.ApplyTo(h);
           if (maxISize < result) {
             result = maxISize;
           }
@@ -5131,7 +5125,7 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis              aAxis,
             (aPercentageBasis.isNothing() &&
              GetPercentBSize(styleMinBSize, aFrame, horizontalAxis, h))) {
           h = std::max(0, h - bSizeTakenByBoxSizing);
-          nscoord minISize = NSCoordMulDiv(h, ratioISize, ratioBSize);
+          nscoord minISize = ratio.ApplyTo(h);
           if (minISize > result) {
             result = minISize;
           }
@@ -6594,12 +6588,12 @@ nsLayoutUtils::DrawSingleImage(gfxContext&            aContext,
 /* static */ void
 nsLayoutUtils::ComputeSizeForDrawing(imgIContainer *aImage,
                                      CSSIntSize&    aImageSize, /*outparam*/
-                                     nsSize&        aIntrinsicRatio, /*outparam*/
+                                     AspectRatio&   aIntrinsicRatio, /*outparam*/
                                      bool&          aGotWidth,  /*outparam*/
                                      bool&          aGotHeight  /*outparam*/)
 {
   aGotWidth  = NS_SUCCEEDED(aImage->GetWidth(&aImageSize.width));
-  aGotHeight = NS_SUCCEEDED(aImage->GetHeight(&aImageSize.height));
+  aGotHeight = NS_SUCCEEDED(aImage->GetHeight(&aImageSize.height)); 
   bool gotRatio = NS_SUCCEEDED(aImage->GetIntrinsicRatio(&aIntrinsicRatio));
 
   if (!(aGotWidth && aGotHeight) && !gotRatio) {
@@ -6607,7 +6601,7 @@ nsLayoutUtils::ComputeSizeForDrawing(imgIContainer *aImage,
     // decoded) and should return zero size.
     aGotWidth = aGotHeight = true;
     aImageSize = CSSIntSize(0, 0);
-    aIntrinsicRatio = nsSize(0, 0);
+    aIntrinsicRatio = AspectRatio();
   }
 }
 
@@ -6616,7 +6610,7 @@ nsLayoutUtils::ComputeSizeForDrawingWithFallback(imgIContainer* aImage,
                                                  const nsSize&  aFallbackSize)
 {
   CSSIntSize imageSize;
-  nsSize imageRatio;
+  AspectRatio imageRatio;
   bool gotHeight, gotWidth;
   ComputeSizeForDrawing(aImage, imageSize, imageRatio, gotWidth, gotHeight);
 
@@ -6624,19 +6618,13 @@ nsLayoutUtils::ComputeSizeForDrawingWithFallback(imgIContainer* aImage,
   // intrinsic ratio of the image.
   if (gotWidth != gotHeight) {
     if (!gotWidth) {
-      if (imageRatio.height != 0) {
-        imageSize.width =
-          NSCoordSaturatingNonnegativeMultiply(imageSize.height,
-                                               float(imageRatio.width) /
-                                               float(imageRatio.height));
+      if (imageRatio) {
+        imageSize.width = imageRatio.ApplyTo(imageSize.height);
         gotWidth = true;
       }
     } else {
-      if (imageRatio.width != 0) {
-        imageSize.height =
-          NSCoordSaturatingNonnegativeMultiply(imageSize.width,
-                                               float(imageRatio.height) /
-                                               float(imageRatio.width));
+      if (imageRatio) {
+        imageSize.height = imageRatio.Inverted().ApplyTo(imageSize.width);
         gotHeight = true;
       }
     }
diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h
index 36a43e46b..21407511a 100644
--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -65,6 +65,7 @@ struct nsStyleImageOrientation;
 struct nsOverflowAreas;
 
 namespace mozilla {
+struct aspectRatio;
 enum class CSSPseudoElementType : uint8_t;
 class EventListenerManager;
 class SVGImageContext;
@@ -126,6 +127,7 @@ enum class RelativeTo {
  */
 class nsLayoutUtils
 {
+  typedef mozilla::AspectRatio AspectRatio;
   typedef mozilla::dom::DOMRectList DOMRectList;
   typedef mozilla::layers::Layer Layer;
   typedef mozilla::ContainerLayerParameters ContainerLayerParameters;
@@ -1217,7 +1219,7 @@ public:
    */
   static nsRect ComputeObjectDestRect(const nsRect& aConstraintRect,
                                       const IntrinsicSize& aIntrinsicSize,
-                                      const nsSize& aIntrinsicRatio,
+                                      const AspectRatio& aIntrinsicRatio,
                                       const nsStylePosition* aStylePos,
                                       nsPoint* aAnchorPoint = nullptr);
 
@@ -1837,7 +1839,7 @@ public:
    */
   static void ComputeSizeForDrawing(imgIContainer* aImage,
                                     CSSIntSize&    aImageSize,
-                                    nsSize&        aIntrinsicRatio,
+                                    AspectRatio&        aIntrinsicRatio,
                                     bool&          aGotWidth,
                                     bool&          aGotHeight);
 
diff --git a/layout/generic/AspectRatio.h b/layout/generic/AspectRatio.h
new file mode 100644
index 000000000..0056c0620
--- /dev/null
+++ b/layout/generic/AspectRatio.h
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_AspectRatio_h
+#define mozilla_AspectRatio_h
+
+/* The aspect ratio of a box, in a "width / height" format. */
+
+#include "mozilla/Attributes.h"
+#include "nsCoord.h"
+#include <algorithm>
+#include <limits>
+
+namespace mozilla {
+
+struct AspectRatio {
+  AspectRatio() : mRatio(0.0f) {}
+  explicit AspectRatio(float aRatio) : mRatio(std::max(aRatio, 0.0f)) {}
+
+  static AspectRatio FromSize(float aWidth, float aHeight) {
+    if (aWidth == 0.0f || aHeight == 0.0f) {
+      return AspectRatio();
+    }
+    return AspectRatio(aWidth / aHeight);
+  }
+
+  static AspectRatio FromSize(nsSize aSize) {
+    return FromSize(aSize.width, aSize.height);
+  }
+
+  static AspectRatio FromSize(nsIntSize aSize) {
+    return FromSize(aSize.width, aSize.height);
+  }
+
+  explicit operator bool() const { return mRatio != 0.0f; }
+
+  nscoord ApplyTo(nscoord aCoord) const {
+    MOZ_DIAGNOSTIC_ASSERT(*this);
+    return NSCoordSaturatingNonnegativeMultiply(aCoord, mRatio);
+  }
+
+  float ApplyToFloat(float aFloat) const {
+    MOZ_DIAGNOSTIC_ASSERT(*this);
+    return mRatio * aFloat;
+  }
+
+  // Inverts the ratio, in order to get the height / width ratio.
+  MOZ_MUST_USE AspectRatio Inverted() const {
+    if (!*this) {
+      return AspectRatio();
+    }
+    // Clamp to a small epsilon, in case mRatio is absurdly large & produces
+    // 0.0f in the division here (so that valid ratios always generate other
+    // valid ratios when inverted).
+    return AspectRatio(
+        std::max(std::numeric_limits<float>::epsilon(), 1.0f / mRatio));
+  }
+
+  bool operator==(const AspectRatio& aOther) const {
+    return mRatio == aOther.mRatio;
+  }
+
+  bool operator!=(const AspectRatio& aOther) const {
+    return !(*this == aOther);
+  }
+
+  bool operator<(const AspectRatio& aOther) const {
+    return mRatio < aOther.mRatio;
+  }
+
+ private:
+  // 0.0f represents no aspect ratio.
+  float mRatio;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_AspectRatio_h
diff --git a/layout/generic/crashtests/1633434.html b/layout/generic/crashtests/1633434.html
new file mode 100644
index 000000000..8a60b2072
--- /dev/null
+++ b/layout/generic/crashtests/1633434.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <script>
+      document.addEventListener('DOMContentLoaded', () => {
+        const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg')
+        svg.setAttribute('height', '6')
+        svg.setAttribute('width', '1pc')
+        document.documentElement.appendChild(svg)
+        svg.style.setProperty('height', '5%', undefined)
+        svg.width.baseVal.valueInSpecifiedUnits = 1.988164037240853e+38
+      })
+    </script>
+</head>
+</html>
diff --git a/layout/generic/crashtests/crashtests.list b/layout/generic/crashtests/crashtests.list
index 1a597e51c..72872bfde 100644
--- a/layout/generic/crashtests/crashtests.list
+++ b/layout/generic/crashtests/crashtests.list
@@ -644,3 +644,4 @@ load 1304441.html
 load 1316649.html
 load 1381134.html
 load 1381134-2.html
+load 1633434.html
diff --git a/layout/generic/moz.build b/layout/generic/moz.build
index ad186ef7a..b830470a3 100644
--- a/layout/generic/moz.build
+++ b/layout/generic/moz.build
@@ -109,6 +109,7 @@ EXPORTS += [
 ]
 
 EXPORTS.mozilla += [
+    'AspectRatio.h',
     'CSSAlignUtils.h',
     'ReflowInput.h',
     'ReflowOutput.h',
diff --git a/layout/generic/nsFlexContainerFrame.cpp b/layout/generic/nsFlexContainerFrame.cpp
index 69200117b..a03d777e7 100644
--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -557,8 +557,8 @@ public:
     return mFlexShrink * mFlexBaseSize;
   }
 
-  const nsSize& IntrinsicRatio() const { return mIntrinsicRatio; }
-  bool HasIntrinsicRatio() const { return mIntrinsicRatio != nsSize(); }
+  const AspectRatio IntrinsicRatio() const { return mIntrinsicRatio; }
+  bool HasIntrinsicRatio() const { return !!mIntrinsicRatio; }
 
   // Getters for margin:
   // ===================
@@ -756,7 +756,7 @@ protected:
   const float mFlexGrow;
   const float mFlexShrink;
 
-  const nsSize mIntrinsicRatio;
+  const AspectRatio mIntrinsicRatio;
 
   const nsMargin mBorderPadding;
   nsMargin mMargin; // non-const because we need to resolve auto margins
@@ -1520,22 +1520,20 @@ CrossSizeToUseWithRatio(const FlexItem& aFlexItem,
 }
 
 // Convenience function; returns a main-size, given a cross-size and an
-// intrinsic ratio. The intrinsic ratio must not have 0 in its cross-axis
-// component (or else we'll divide by 0).
+// intrinsic ratio. The caller is responsible for ensuring that the passed-in
+// intrinsic ratio is not zero.
 static nscoord
 MainSizeFromAspectRatio(nscoord aCrossSize,
-                        const nsSize& aIntrinsicRatio,
+                        const AspectRatio& aIntrinsicRatio,
                         const FlexboxAxisTracker& aAxisTracker)
 {
-  MOZ_ASSERT(aAxisTracker.GetCrossComponent(aIntrinsicRatio) != 0,
+  MOZ_ASSERT(aIntrinsicRatio,
              "Invalid ratio; will divide by 0! Caller should've checked...");
+  AspectRatio ratio = aAxisTracker.IsMainAxisHorizontal() ?
+                      aIntrinsicRatio :
+                      aIntrinsicRatio.Inverted();
 
-  if (aAxisTracker.IsCrossAxisHorizontal()) {
-    // cross axis horiz --> aCrossSize is a width. Converting to height.
-    return NSCoordMulDiv(aCrossSize, aIntrinsicRatio.height, aIntrinsicRatio.width);
-  }
-  // cross axis vert --> aCrossSize is a height. Converting to width.
-  return NSCoordMulDiv(aCrossSize, aIntrinsicRatio.width, aIntrinsicRatio.height);
+  return ratio.ApplyTo(aCrossSize);
 }
 
 // Partially resolves "min-[width|height]:auto" and returns the resulting value.
@@ -1584,7 +1582,7 @@ PartiallyResolveAutoMinSize(const FlexItem& aFlexItem,
   // * if the item has an intrinsic aspect ratio, the width (height) calculated
   //   from the aspect ratio and any definite size constraints in the opposite
   //   dimension.
-  if (aAxisTracker.GetCrossComponent(aFlexItem.IntrinsicRatio()) != 0) {
+  if (aFlexItem.IntrinsicRatio()) {
     // We have a usable aspect ratio. (not going to divide by 0)
     const bool useMinSizeIfCrossSizeIsIndefinite = true;
     nscoord crossSizeToUseWithRatio =
@@ -1617,7 +1615,7 @@ ResolveAutoFlexBasisFromRatio(FlexItem& aFlexItem,
   //  - a definite cross size
   // then the flex base size is calculated from its inner cross size and the
   // flex item’s intrinsic aspect ratio.
-  if (aAxisTracker.GetCrossComponent(aFlexItem.IntrinsicRatio()) != 0) {
+  if (aFlexItem.IntrinsicRatio()) {
     // We have a usable aspect ratio. (not going to divide by 0)
     const bool useMinSizeIfCrossSizeIsIndefinite = false;
     nscoord crossSizeToUseWithRatio =
@@ -1693,8 +1691,7 @@ nsFlexContainerFrame::
     // (We'll consider that later, if we need to.)
     resolvedMinSize = PartiallyResolveAutoMinSize(aFlexItem, aItemReflowInput,
                                                   aAxisTracker);
-    if (resolvedMinSize > 0 &&
-        aAxisTracker.GetCrossComponent(aFlexItem.IntrinsicRatio()) == 0) {
+    if (resolvedMinSize > 0 && !aFlexItem.IntrinsicRatio()) {
       // We don't have a usable aspect ratio, so we need to consider our
       // min-content size as another candidate min-size, which we'll have to
       // min() with the current resolvedMinSize.
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index dd7933b03..72923c4b7 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -4641,10 +4641,10 @@ nsFrame::GetIntrinsicSize()
   return IntrinsicSize(); // default is width/height set to eStyleUnit_None
 }
 
-/* virtual */ nsSize
+/* virtual */ AspectRatio
 nsFrame::GetIntrinsicRatio()
 {
-  return nsSize(0, 0);
+  return AspectRatio();
 }
 
 /* virtual */
@@ -4658,7 +4658,7 @@ nsFrame::ComputeSize(nsRenderingContext* aRenderingContext,
                      const LogicalSize&  aPadding,
                      ComputeSizeFlags    aFlags)
 {
-  MOZ_ASSERT(GetIntrinsicRatio() == nsSize(0,0),
+  MOZ_ASSERT(!GetIntrinsicRatio(),
              "Please override this method and call "
              "nsFrame::ComputeSizeWithIntrinsicDimensions instead.");
   LogicalSize result = ComputeAutoSize(aRenderingContext, aWM,
@@ -4914,13 +4914,15 @@ LogicalSize
 nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingContext,
                                             WritingMode          aWM,
                                             const IntrinsicSize& aIntrinsicSize,
-                                            nsSize               aIntrinsicRatio,
+                                            const AspectRatio&   aIntrinsicRatio,
                                             const LogicalSize&   aCBSize,
                                             const LogicalSize&   aMargin,
                                             const LogicalSize&   aBorder,
                                             const LogicalSize&   aPadding,
                                             ComputeSizeFlags     aFlags)
 {
+  auto logicalRatio =
+      aWM.IsVertical() ? aIntrinsicRatio.Inverted() : aIntrinsicRatio;
   const nsStylePosition* stylePos = StylePosition();
   const nsStyleCoord* inlineStyleCoord = &stylePos->ISize(aWM);
   const nsStyleCoord* blockStyleCoord = &stylePos->BSize(aWM);
@@ -5181,10 +5183,6 @@ nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingConte
     intrinsicBSize = 0;
   }
 
-  NS_ASSERTION(aIntrinsicRatio.width >= 0 && aIntrinsicRatio.height >= 0,
-               "Intrinsic ratio has a negative component!");
-  LogicalSize logicalRatio(aWM, aIntrinsicRatio);
-
   // Now calculate the used values for iSize and bSize:
 
   if (isAutoISize) {
@@ -5198,9 +5196,9 @@ nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingConte
 
       if (hasIntrinsicISize) {
         tentISize = intrinsicISize;
-      } else if (hasIntrinsicBSize && logicalRatio.BSize(aWM) > 0) {
-        tentISize = NSCoordMulDiv(intrinsicBSize, logicalRatio.ISize(aWM), logicalRatio.BSize(aWM));
-      } else if (logicalRatio.ISize(aWM) > 0) {
+      } else if (hasIntrinsicBSize && logicalRatio) {
+        tentISize = logicalRatio.ApplyTo(intrinsicBSize);
+      } else if (logicalRatio) {
         tentISize = aCBSize.ISize(aWM) - boxSizingToMarginEdgeISize; // XXX scrollbar?
         if (tentISize < 0) tentISize = 0;
       } else {
@@ -5217,8 +5215,8 @@ nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingConte
 
       if (hasIntrinsicBSize) {
         tentBSize = intrinsicBSize;
-      } else if (logicalRatio.ISize(aWM) > 0) {
-        tentBSize = NSCoordMulDiv(tentISize, logicalRatio.BSize(aWM), logicalRatio.ISize(aWM));
+      } else if (logicalRatio) {
+        tentBSize = logicalRatio.Inverted().ApplyTo(tentISize);
       } else {
         tentBSize = nsPresContext::CSSPixelsToAppUnits(150);
       }
@@ -5229,46 +5227,39 @@ nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingConte
         stretchB = (stretchI == eStretch ? eStretch : eStretchPreservingRatio);
       }
 
-      if (aIntrinsicRatio != nsSize(0, 0)) {
+      if (logicalRatio) {
         if (stretchI == eStretch) {
           tentISize = iSize;  // * / 'stretch'
           if (stretchB == eStretch) {
             tentBSize = bSize;  // 'stretch' / 'stretch'
-          } else if (stretchB == eStretchPreservingRatio && logicalRatio.ISize(aWM) > 0) {
+          } else if (stretchB == eStretchPreservingRatio) {
             // 'normal' / 'stretch'
-            tentBSize = NSCoordMulDiv(iSize, logicalRatio.BSize(aWM), logicalRatio.ISize(aWM));
+            tentBSize = logicalRatio.Inverted().ApplyTo(iSize);
           }
         } else if (stretchB == eStretch) {
           tentBSize = bSize;  // 'stretch' / * (except 'stretch')
-          if (stretchI == eStretchPreservingRatio && logicalRatio.BSize(aWM) > 0) {
+          if (stretchI == eStretchPreservingRatio) {
             // 'stretch' / 'normal'
-            tentISize = NSCoordMulDiv(bSize, logicalRatio.ISize(aWM), logicalRatio.BSize(aWM));
+            tentISize = logicalRatio.ApplyTo(bSize);
           }
         } else if (stretchI == eStretchPreservingRatio) {
           tentISize = iSize;  // * (except 'stretch') / 'normal'
-          if (logicalRatio.ISize(aWM) > 0) {
-            tentBSize = NSCoordMulDiv(iSize, logicalRatio.BSize(aWM), logicalRatio.ISize(aWM));
-          }
+          tentBSize = logicalRatio.Inverted().ApplyTo(iSize);
           if (stretchB == eStretchPreservingRatio && tentBSize > bSize) {
             // Stretch within the CB size with preserved intrinsic ratio.
             tentBSize = bSize;  // 'normal' / 'normal'
-            if (logicalRatio.BSize(aWM) > 0) {
-              tentISize = NSCoordMulDiv(bSize, logicalRatio.ISize(aWM), logicalRatio.BSize(aWM));
-            }
+            tentISize = logicalRatio.ApplyTo(bSize);
           }
         } else if (stretchB == eStretchPreservingRatio) {
           tentBSize = bSize;  // 'normal' / * (except 'normal' and 'stretch')
-          if (logicalRatio.BSize(aWM) > 0) {
-            tentISize = NSCoordMulDiv(bSize, logicalRatio.ISize(aWM), logicalRatio.BSize(aWM));
-          }
+          tentISize = logicalRatio.ApplyTo(bSize);
         }
       }
 
       // ComputeAutoSizeWithIntrinsicDimensions preserves the ratio when applying
       // the min/max-size.  We don't want that when we have 'stretch' in either
       // axis because tentISize/tentBSize is likely not according to ratio now.
-      if (aIntrinsicRatio != nsSize(0, 0) &&
-          stretchI != eStretch && stretchB != eStretch) {
+      if (logicalRatio && stretchI != eStretch && stretchB != eStretch) {
         nsSize autoSize = nsLayoutUtils::
           ComputeAutoSizeWithIntrinsicDimensions(minISize, minBSize,
                                                  maxISize, maxBSize,
@@ -5289,8 +5280,8 @@ nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingConte
       // 'auto' iSize, non-'auto' bSize
       bSize = NS_CSS_MINMAX(bSize, minBSize, maxBSize);
       if (stretchI != eStretch) {
-        if (logicalRatio.BSize(aWM) > 0) {
-          iSize = NSCoordMulDiv(bSize, logicalRatio.ISize(aWM), logicalRatio.BSize(aWM));
+        if (logicalRatio) {
+          iSize = logicalRatio.ApplyTo(bSize);
         } else if (hasIntrinsicISize) {
           if (!((aFlags & ComputeSizeFlags::eIClampMarginBoxMinSize) &&
                 intrinsicISize > iSize)) {
@@ -5309,8 +5300,8 @@ nsFrame::ComputeSizeWithIntrinsicDimensions(nsRenderingContext*  aRenderingConte
       // non-'auto' iSize, 'auto' bSize
       iSize = NS_CSS_MINMAX(iSize, minISize, maxISize);
       if (stretchB != eStretch) {
-        if (logicalRatio.ISize(aWM) > 0) {
-          bSize = NSCoordMulDiv(iSize, logicalRatio.BSize(aWM), logicalRatio.ISize(aWM));
+        if (logicalRatio) {
+          bSize = logicalRatio.Inverted().ApplyTo(iSize);
         } else if (hasIntrinsicBSize) {
           if (!((aFlags & ComputeSizeFlags::eBClampMarginBoxMinSize) &&
                 intrinsicBSize > bSize)) {
diff --git a/layout/generic/nsFrame.h b/layout/generic/nsFrame.h
index 439e39856..d75555fec 100644
--- a/layout/generic/nsFrame.h
+++ b/layout/generic/nsFrame.h
@@ -264,7 +264,7 @@ public:
   IntrinsicISizeOffsetData
   IntrinsicISizeOffsets(nscoord aPercentageBasis = NS_UNCONSTRAINEDSIZE) override;
   virtual mozilla::IntrinsicSize GetIntrinsicSize() override;
-  virtual nsSize GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
 
   virtual mozilla::LogicalSize
   ComputeSize(nsRenderingContext*         aRenderingContext,
@@ -285,7 +285,7 @@ public:
               nsRenderingContext*           aRenderingContext,
               mozilla::WritingMode          aWM,
               const mozilla::IntrinsicSize& aIntrinsicSize,
-              nsSize                        aIntrinsicRatio,
+              const mozilla::AspectRatio&   aIntrinsicRatio,
               const mozilla::LogicalSize&   aCBSize,
               const mozilla::LogicalSize&   aMargin,
               const mozilla::LogicalSize&   aBorder,
diff --git a/layout/generic/nsHTMLCanvasFrame.cpp b/layout/generic/nsHTMLCanvasFrame.cpp
index f86ec1136..f40f799ba 100644
--- a/layout/generic/nsHTMLCanvasFrame.cpp
+++ b/layout/generic/nsHTMLCanvasFrame.cpp
@@ -44,21 +44,6 @@ IntrinsicSizeFromCanvasSize(const nsIntSize& aCanvasSizeInPx)
   return intrinsicSize;
 }
 
-/* Helper for our nsIFrame::GetIntrinsicRatio() impl. Takes the result of
- * "GetCanvasSize()" as a parameter, which may help avoid redundant
- * indirect calls to GetCanvasSize().
- *
- * @param aCanvasSizeInPx The canvas's size in CSS pixels, as returned
- *                        by GetCanvasSize().
- * @return The canvas's intrinsic ratio, as a nsSize.
- */
-static nsSize
-IntrinsicRatioFromCanvasSize(const nsIntSize& aCanvasSizeInPx)
-{
-  return nsSize(nsPresContext::CSSPixelsToAppUnits(aCanvasSizeInPx.width),
-                nsPresContext::CSSPixelsToAppUnits(aCanvasSizeInPx.height));
-}
-
 class nsDisplayCanvas : public nsDisplayItem {
 public:
   nsDisplayCanvas(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
@@ -92,7 +77,7 @@ public:
       // Need intrinsic size & ratio, for ComputeObjectDestRect:
       nsIntSize canvasSize = f->GetCanvasSize();
       IntrinsicSize intrinsicSize = IntrinsicSizeFromCanvasSize(canvasSize);
-      nsSize intrinsicRatio = IntrinsicRatioFromCanvasSize(canvasSize);
+      AspectRatio intrinsicRatio = AspectRatio::FromSize(canvasSize);
 
       const nsRect destRect =
         nsLayoutUtils::ComputeObjectDestRect(constraintRect,
@@ -211,10 +196,16 @@ nsHTMLCanvasFrame::GetIntrinsicSize()
   return IntrinsicSizeFromCanvasSize(GetCanvasSize());
 }
 
-/* virtual */ nsSize
+/* virtual */ AspectRatio
 nsHTMLCanvasFrame::GetIntrinsicRatio()
 {
-  return IntrinsicRatioFromCanvasSize(GetCanvasSize());
+ // When 'contain: size' is implemented, make sure to check for it.
+/*
+  if (StyleDisplay()->IsContainSize()) {
+    return AspectRatio();
+  }
+ */
+  return AspectRatio::FromSize(GetCanvasSize());
 }
 
 /* virtual */
@@ -234,7 +225,7 @@ nsHTMLCanvasFrame::ComputeSize(nsRenderingContext *aRenderingContext,
   intrinsicSize.width.SetCoordValue(nsPresContext::CSSPixelsToAppUnits(size.width));
   intrinsicSize.height.SetCoordValue(nsPresContext::CSSPixelsToAppUnits(size.height));
 
-  nsSize intrinsicRatio = GetIntrinsicRatio(); // won't actually be used
+  AspectRatio intrinsicRatio = GetIntrinsicRatio();
 
   return ComputeSizeWithIntrinsicDimensions(aRenderingContext, aWM,
                                             intrinsicSize, intrinsicRatio,
@@ -340,7 +331,7 @@ nsHTMLCanvasFrame::BuildLayer(nsDisplayListBuilder* aBuilder,
     return nullptr;
 
   IntrinsicSize intrinsicSize = IntrinsicSizeFromCanvasSize(canvasSizeInPx);
-  nsSize intrinsicRatio = IntrinsicRatioFromCanvasSize(canvasSizeInPx);
+  AspectRatio intrinsicRatio = AspectRatio::FromSize(canvasSizeInPx);
 
   nsRect dest =
     nsLayoutUtils::ComputeObjectDestRect(area, intrinsicSize, intrinsicRatio,
diff --git a/layout/generic/nsHTMLCanvasFrame.h b/layout/generic/nsHTMLCanvasFrame.h
index b2d159627..8432ad224 100644
--- a/layout/generic/nsHTMLCanvasFrame.h
+++ b/layout/generic/nsHTMLCanvasFrame.h
@@ -58,7 +58,7 @@ public:
   virtual nscoord GetMinISize(nsRenderingContext *aRenderingContext) override;
   virtual nscoord GetPrefISize(nsRenderingContext *aRenderingContext) override;
   virtual mozilla::IntrinsicSize GetIntrinsicSize() override;
-  virtual nsSize GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
 
   virtual mozilla::LogicalSize
   ComputeSize(nsRenderingContext *aRenderingContext,
diff --git a/layout/generic/nsIFrame.h b/layout/generic/nsIFrame.h
index dfe83bcbe..d54ddc2b5 100644
--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -27,6 +27,7 @@
 #include "FrameProperties.h"
 #include "LayoutConstants.h"
 #include "mozilla/layout/FrameChildList.h"
+#include "mozilla/AspectRatio.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/WritingModes.h"
 #include "nsDirection.h"
@@ -2063,15 +2064,14 @@ public:
   virtual mozilla::IntrinsicSize GetIntrinsicSize() = 0;
 
   /**
-   * Get the intrinsic ratio of this element, or nsSize(0,0) if it has
-   * no intrinsic ratio.  The intrinsic ratio is the ratio of the
-   * height/width of a box with an intrinsic size or the intrinsic
-   * aspect ratio of a scalable vector image without an intrinsic size.
+   * Get the intrinsic ratio of this element, or a default-constructed
+   * AspectRatio if it has no intrinsic ratio.
    *
-   * Either one of the sides may be zero, indicating a zero or infinite
-   * ratio.
+   * The intrinsic ratio is the ratio of the width/height of a box with an
+   * intrinsic size or the intrinsic aspect ratio of a scalable vector image
+   * without an intrinsic size.
    */
-  virtual nsSize GetIntrinsicRatio() = 0;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() = 0;
 
   /**
    * Bit-flags to pass to ComputeSize in |aFlags| parameter.
diff --git a/layout/generic/nsImageFrame.cpp b/layout/generic/nsImageFrame.cpp
index b96af66b5..d6f47f2e4 100644
--- a/layout/generic/nsImageFrame.cpp
+++ b/layout/generic/nsImageFrame.cpp
@@ -14,6 +14,7 @@
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/Helpers.h"
 #include "mozilla/gfx/PathHelpers.h"
+#include "mozilla/dom/HTMLImageElement.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/Unused.h"
 
@@ -138,7 +139,6 @@ NS_IMPL_FRAMEARENA_HELPERS(nsImageFrame)
 nsImageFrame::nsImageFrame(nsStyleContext* aContext) :
   nsAtomicContainerFrame(aContext),
   mComputedSize(0, 0),
-  mIntrinsicRatio(0, 0),
   mDisplayingIcon(false),
   mFirstFrameComplete(false),
   mReflowCallbackPosted(false),
@@ -230,26 +230,26 @@ nsImageFrame::DidSetStyleContext(nsStyleContext* aOldStyleContext)
 {
   nsAtomicContainerFrame::DidSetStyleContext(aOldStyleContext);
 
-  if (!mImage) {
-    // We'll pick this change up whenever we do get an image.
-    return;
-  }
-
   nsStyleImageOrientation newOrientation = StyleVisibility()->mImageOrientation;
 
   // We need to update our orientation either if we had no style context before
   // because this is the first time it's been set, or if the image-orientation
   // property changed from its previous value.
   bool shouldUpdateOrientation =
-    !aOldStyleContext ||
-    aOldStyleContext->StyleVisibility()->mImageOrientation != newOrientation;
+    mImage &&
+    (!aOldStyleContext ||
+     aOldStyleContext->StyleVisibility()->mImageOrientation != newOrientation);
 
   if (shouldUpdateOrientation) {
     nsCOMPtr<imgIContainer> image(mImage->Unwrap());
     mImage = nsLayoutUtils::OrientImage(image, newOrientation);
 
-    UpdateIntrinsicSize(mImage);
-    UpdateIntrinsicRatio(mImage);
+    UpdateIntrinsicSize();
+    UpdateIntrinsicRatio();
+  } else if (!aOldStyleContext ||
+             aOldStyleContext->StylePosition()->mAspectRatio !=
+                 StylePosition()->mAspectRatio) {
+    UpdateIntrinsicRatio();
   }
 }
 
@@ -287,50 +287,110 @@ nsImageFrame::Init(nsIContent*       aContent,
     p->AdjustPriority(-1);
 }
 
-bool
-nsImageFrame::UpdateIntrinsicSize(imgIContainer* aImage)
+static IntrinsicSize
+ComputeIntrinsicSize(imgIContainer* aImage,
+                     bool aUseMappedRatio,
+                     const nsImageFrame& aFrame)
 {
-  NS_PRECONDITION(aImage, "null image");
-  if (!aImage)
-    return false;
+ // When 'contain: size' is implemented, make sure to check for it.
+/*
+  const ComputedStyle& style = *aFrame.Style();
+  if (style.StyleDisplay()->IsContainSize()) {
+    return AspectRatio();
+  }
+ */
+  nsSize size;
+  IntrinsicSize intrinsicSize;
+  if (aImage && NS_SUCCEEDED(aImage->GetIntrinsicSize(&size))) {
+    if (size.width != -1)
+      intrinsicSize.width.SetCoordValue(size.width);
+    if (size.height != -1)
+      intrinsicSize.height.SetCoordValue(size.height);
+    return intrinsicSize;
+  }
 
-  IntrinsicSize oldIntrinsicSize = mIntrinsicSize;
-  mIntrinsicSize = IntrinsicSize();
-
-  // Set intrinsic size to match aImage's reported intrinsic width & height.
-  nsSize intrinsicSize;
-  if (NS_SUCCEEDED(aImage->GetIntrinsicSize(&intrinsicSize))) {
-    // If the image has no intrinsic width, intrinsicSize.width will be -1, and
-    // we can leave mIntrinsicSize.width at its default value of eStyleUnit_None.
-    // Otherwise we use intrinsicSize.width. Height works the same way.
-    if (intrinsicSize.width != -1)
-      mIntrinsicSize.width.SetCoordValue(intrinsicSize.width);
-    if (intrinsicSize.height != -1)
-      mIntrinsicSize.height.SetCoordValue(intrinsicSize.height);
-  } else {
-    // Failure means that the image hasn't loaded enough to report a result. We
-    // treat this case as if the image's intrinsic size was 0x0.
-    mIntrinsicSize.width.SetCoordValue(0);
-    mIntrinsicSize.height.SetCoordValue(0);
+  // If broken images should ever lose their size
+  /*
+  if (aFrame.ShouldShowBrokenImageIcon()) {
+    nscoord edgeLengthToUse = nsPresContext::CSSPixelsToAppUnits(
+        ICON_SIZE + (2 * (ICON_PADDING + ALT_BORDER_WIDTH)));
+    intrinsicSize.width.SetCoordValue(edgeLengthToUse);
+    intrinsicSize.height.SetCoordValue(edgeLengthToUse);
+    return intrinsicSize;
   }
+  */
 
-  return mIntrinsicSize != oldIntrinsicSize;
+  if (aUseMappedRatio && aFrame.StylePosition()->mAspectRatio != 0.0f) {
+    return IntrinsicSize();
+  }
+
+  intrinsicSize.width.SetCoordValue(0);
+  intrinsicSize.height.SetCoordValue(0);
+  return intrinsicSize;
+}
+
+// For compat reasons, see bug 1602047, we don't use the intrinsic ratio from
+// width="" and height="" for images with no src attribute (no request).
+//
+// If <img loading=lazy> ever gets implemented, this will need to check for it.
+bool nsImageFrame::ShouldUseMappedAspectRatio() const {
+  nsCOMPtr<imgIRequest> currentRequest;
+  nsCOMPtr<nsIImageLoadingContent> imageLoader = do_QueryInterface(mContent);
+  if (imageLoader) {
+    imageLoader->GetRequest(nsIImageLoadingContent::CURRENT_REQUEST,
+                            getter_AddRefs(currentRequest));
+  }
+  if (!!currentRequest) {
+    return true;
+  }
+  // TODO(emilio): Investigate the compat situation of the above check, maybe we
+  // can just check for empty src attribute or something...
+  auto* image = static_cast<HTMLImageElement*>(mContent);
+  return image && image->IsAwaitingLoad();
 }
 
 bool
-nsImageFrame::UpdateIntrinsicRatio(imgIContainer* aImage)
+nsImageFrame::UpdateIntrinsicSize()
 {
-  NS_PRECONDITION(aImage, "null image");
-
-  if (!aImage)
-    return false;
+  IntrinsicSize oldIntrinsicSize = mIntrinsicSize;
+  mIntrinsicSize = ComputeIntrinsicSize(mImage, ShouldUseMappedAspectRatio(), *this);
+  return mIntrinsicSize != oldIntrinsicSize;
+}
 
-  nsSize oldIntrinsicRatio = mIntrinsicRatio;
+static AspectRatio
+ComputeAspectRatio(imgIContainer* aImage,
+                   bool aUseMappedRatio,
+                   const nsImageFrame& aFrame)
+{
+ // When 'contain: size' is implemented, make sure to check for it.
+/*
+  const ComputedStyle& style = *aFrame.Style();
+  if (style.StyleDisplay()->IsContainSize()) {
+    return AspectRatio();
+  }
+ */
+  if (aImage) {
+    AspectRatio fromImage;
+    if (NS_SUCCEEDED(aImage->GetIntrinsicRatio(&fromImage))) {
+      return fromImage;
+    }
+  }
+  if (aUseMappedRatio && aFrame.StylePosition()->mAspectRatio != 0.0f) {
+    return AspectRatio(aFrame.StylePosition()->mAspectRatio);
+  }
+  if (aFrame.ShouldShowBrokenImageIcon()) {
+    return AspectRatio(1.0f);
+  }
+  return AspectRatio();
+}
 
-  // Set intrinsic ratio to match aImage's reported intrinsic ratio.
-  if (NS_FAILED(aImage->GetIntrinsicRatio(&mIntrinsicRatio)))
-    mIntrinsicRatio.SizeTo(0, 0);
+bool
+nsImageFrame::UpdateIntrinsicRatio()
+{
 
+  AspectRatio oldIntrinsicRatio = mIntrinsicRatio;
+  mIntrinsicRatio =
+      ComputeAspectRatio(mImage, ShouldUseMappedAspectRatio(), *this);
   return mIntrinsicRatio != oldIntrinsicRatio;
 }
 
@@ -542,30 +602,38 @@ nsImageFrame::OnSizeAvailable(imgIRequest* aRequest, imgIContainer* aImage)
     return NS_OK;
   }
 
-  bool intrinsicSizeChanged = false;
+  UpdateImage(aRequest, aImage);
+  return NS_OK;
+}
+
+void nsImageFrame::UpdateImage(imgIRequest* aRequest, imgIContainer* aImage) {
+  MOZ_ASSERT(aRequest);
   if (SizeIsAvailable(aRequest)) {
     // This is valid and for the current request, so update our stored image
     // container, orienting according to our style.
-    mImage = nsLayoutUtils::OrientImage(aImage, StyleVisibility()->mImageOrientation);
-
-    intrinsicSizeChanged = UpdateIntrinsicSize(mImage);
-    intrinsicSizeChanged = UpdateIntrinsicRatio(mImage) || intrinsicSizeChanged;
+    mImage = nsLayoutUtils::OrientImage(aImage,
+                                        StyleVisibility()->mImageOrientation);
+    MOZ_ASSERT(mImage);
   } else {
     // We no longer have a valid image, so release our stored image container.
     mImage = mPrevImage = nullptr;
-
-    // Have to size to 0,0 so that GetDesiredSize recalculates the size.
-    mIntrinsicSize.width.SetCoordValue(0);
-    mIntrinsicSize.height.SetCoordValue(0);
-    mIntrinsicRatio.SizeTo(0, 0);
-    intrinsicSizeChanged = true;
+  }
+  // NOTE(emilio): Intentionally using `|` instead of `||` to avoid
+  // short-circuiting.
+  bool intrinsicSizeChanged =
+      UpdateIntrinsicSize() | UpdateIntrinsicRatio();
+  if (!(mState & IMAGE_GOTINITIALREFLOW)) {
+    return;
   }
 
-  if (intrinsicSizeChanged && (mState & IMAGE_GOTINITIALREFLOW)) {
+  // We're going to need to repaint now either way.
+  InvalidateFrame();
+
+  if (intrinsicSizeChanged) {
     // Now we need to reflow if we have an unconstrained size and have
-    // already gotten the initial reflow
+    // already gotten the initial reflow.
     if (!(mState & IMAGE_SIZECONSTRAINED)) { 
-      nsIPresShell *presShell = presContext->GetPresShell();
+      nsIPresShell *presShell = PresContext()->GetPresShell();
       NS_ASSERTION(presShell, "No PresShell.");
       if (presShell) { 
         presShell->FrameNeedsReflow(this, nsIPresShell::eStyleChange,
@@ -579,8 +647,6 @@ nsImageFrame::OnSizeAvailable(imgIRequest* aRequest, imgIContainer* aImage)
 
     mPrevImage = nullptr;
   }
-
-  return NS_OK;
 }
 
 nsresult
@@ -655,45 +721,9 @@ nsImageFrame::NotifyNewCurrentRequest(imgIRequest *aRequest,
 {
   nsCOMPtr<imgIContainer> image;
   aRequest->GetImage(getter_AddRefs(image));
-  NS_ASSERTION(image || NS_FAILED(aStatus), "Successful load with no container?");
-
-  // May have to switch sizes here!
-  bool intrinsicSizeChanged = true;
-  if (NS_SUCCEEDED(aStatus) && image && SizeIsAvailable(aRequest)) {
-    // Update our stored image container, orienting according to our style.
-    mImage = nsLayoutUtils::OrientImage(image, StyleVisibility()->mImageOrientation);
-
-    intrinsicSizeChanged = UpdateIntrinsicSize(mImage);
-    intrinsicSizeChanged = UpdateIntrinsicRatio(mImage) || intrinsicSizeChanged;
-  } else {
-    // We no longer have a valid image, so release our stored image container.
-    mImage = mPrevImage = nullptr;
-
-    // Have to size to 0,0 so that GetDesiredSize recalculates the size
-    mIntrinsicSize.width.SetCoordValue(0);
-    mIntrinsicSize.height.SetCoordValue(0);
-    mIntrinsicRatio.SizeTo(0, 0);
-  }
-
-  if (mState & IMAGE_GOTINITIALREFLOW) { // do nothing if we haven't gotten the initial reflow yet
-    if (intrinsicSizeChanged) {
-      if (!(mState & IMAGE_SIZECONSTRAINED)) {
-        nsIPresShell *presShell = PresContext()->GetPresShell();
-        if (presShell) {
-          presShell->FrameNeedsReflow(this, nsIPresShell::eStyleChange,
-                                      NS_FRAME_IS_DIRTY);
-        }
-      } else {
-        // We've already gotten the initial reflow, and our size hasn't changed,
-        // so we're ready to request a decode.
-        MaybeDecodeForPredictedSize();
-      }
-
-      mPrevImage = nullptr;
-    }
-    // Update border+content to account for image change
-    InvalidateFrame();
-  }
+  NS_ASSERTION(image || NS_FAILED(aStatus),
+               "Successful load with no container?");
+  UpdateImage(aRequest, image);
 }
 
 void
@@ -787,32 +817,27 @@ bool nsImageFrame::ShouldShowBrokenImageIcon() const
 void
 nsImageFrame::EnsureIntrinsicSizeAndRatio()
 {
+ // When 'contain: size' is implemented, make sure to check for it.
+/*
+  if (StyleDisplay()->IsContainSize()) {
+    // If we have 'contain:size', then our intrinsic size and ratio are 0,0
+    // regardless of what our underlying image may think.
+    mIntrinsicSize = IntrinsicSize(0, 0);
+    mIntrinsicRatio = AspectRatio();
+    return;
+  }
+ */
+
   // If mIntrinsicSize.width and height are 0, then we need to update from the
   // image container.
-  if (mIntrinsicSize.width.GetUnit() == eStyleUnit_Coord &&
+  if (!(mIntrinsicSize.width.GetUnit() == eStyleUnit_Coord &&
       mIntrinsicSize.width.GetCoordValue() == 0 &&
       mIntrinsicSize.height.GetUnit() == eStyleUnit_Coord &&
-      mIntrinsicSize.height.GetCoordValue() == 0) {
-
-    if (mImage) {
-      UpdateIntrinsicSize(mImage);
-      UpdateIntrinsicRatio(mImage);
-    } else {
-      // Image request is null or image size not known.
-      if (!(GetStateBits() & NS_FRAME_GENERATED_CONTENT)) {
-        // Likely an invalid image. Check if we should display it as broken.
-        if (ShouldShowBrokenImageIcon()) {
-          // Invalid image specified. make the image big enough for the "broken" icon
-          nscoord edgeLengthToUse =
-            nsPresContext::CSSPixelsToAppUnits(
-              ICON_SIZE + (2 * (ICON_PADDING + ALT_BORDER_WIDTH)));
-          mIntrinsicSize.width.SetCoordValue(edgeLengthToUse);
-          mIntrinsicSize.height.SetCoordValue(edgeLengthToUse);
-          mIntrinsicRatio.SizeTo(1, 1);
-        }
-      }
-    }
+      mIntrinsicSize.height.GetCoordValue() == 0)) {
+    return;
   }
+  UpdateIntrinsicSize();
+  UpdateIntrinsicRatio();
 }
 
 /* virtual */
@@ -932,7 +957,7 @@ nsImageFrame::GetIntrinsicSize()
   return mIntrinsicSize;
 }
 
-/* virtual */ nsSize
+/* virtual */ AspectRatio
 nsImageFrame::GetIntrinsicRatio()
 {
   return mIntrinsicRatio;
diff --git a/layout/generic/nsImageFrame.h b/layout/generic/nsImageFrame.h
index 59af1be32..5e9b67274 100644
--- a/layout/generic/nsImageFrame.h
+++ b/layout/generic/nsImageFrame.h
@@ -86,7 +86,7 @@ public:
   virtual nscoord GetMinISize(nsRenderingContext *aRenderingContext) override;
   virtual nscoord GetPrefISize(nsRenderingContext *aRenderingContext) override;
   virtual mozilla::IntrinsicSize GetIntrinsicSize() override;
-  virtual nsSize GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
   virtual void Reflow(nsPresContext*           aPresContext,
                       ReflowOutput&     aDesiredSize,
                       const ReflowInput& aReflowInput,
@@ -273,21 +273,19 @@ private:
   void GetDocumentCharacterSet(nsACString& aCharset) const;
   bool ShouldDisplaySelection();
 
+  // Whether the image frame should use the mapped aspect ratio from width=""
+  // and height="".
+  bool ShouldUseMappedAspectRatio() const;
+
   /**
    * Recalculate mIntrinsicSize from the image.
-   *
-   * @return whether aImage's size did _not_
-   *         match our previous intrinsic size.
    */
-  bool UpdateIntrinsicSize(imgIContainer* aImage);
+  bool UpdateIntrinsicSize();
 
   /**
    * Recalculate mIntrinsicRatio from the image.
-   *
-   * @return whether aImage's ratio did _not_
-   *         match our previous intrinsic ratio.
    */
-  bool UpdateIntrinsicRatio(imgIContainer* aImage);
+  bool UpdateIntrinsicRatio();
 
   /**
    * This function calculates the transform for converting between
@@ -308,6 +306,12 @@ private:
   bool IsPendingLoad(imgIRequest* aRequest) const;
 
   /**
+   * Updates mImage based on the current image request (cannot be null), and the
+   * image passed in (can be null), and invalidate layout and paint as needed.
+   */
+  void UpdateImage(imgIRequest* aRequest, imgIContainer* aImage);
+
+  /**
    * Function to convert a dirty rect in the source image to a dirty
    * rect for the image frame.
    */
@@ -333,7 +337,7 @@ private:
   nsCOMPtr<imgIContainer> mPrevImage;
   nsSize mComputedSize;
   mozilla::IntrinsicSize mIntrinsicSize;
-  nsSize mIntrinsicRatio;
+  mozilla::AspectRatio mIntrinsicRatio;
 
   bool mDisplayingIcon;
   bool mFirstFrameComplete;
diff --git a/layout/generic/nsLineLayout.cpp b/layout/generic/nsLineLayout.cpp
index 6a15a9cfa..60e4e8c96 100644
--- a/layout/generic/nsLineLayout.cpp
+++ b/layout/generic/nsLineLayout.cpp
@@ -784,7 +784,7 @@ IsPercentageAware(const nsIFrame* aFrame)
     //   is calculated from the constraint equation used for
     //   block-level, non-replaced elements in normal flow. 
     nsIFrame *f = const_cast<nsIFrame*>(aFrame);
-    if (f->GetIntrinsicRatio() != nsSize(0, 0) &&
+    if (f->GetIntrinsicRatio() &&
         // Some percents are treated like 'auto', so check != coord
         pos->mHeight.GetUnit() != eStyleUnit_Coord) {
       const IntrinsicSize &intrinsicSize = f->GetIntrinsicSize();
diff --git a/layout/generic/nsSubDocumentFrame.cpp b/layout/generic/nsSubDocumentFrame.cpp
index fd9a7d32c..31d04a335 100644
--- a/layout/generic/nsSubDocumentFrame.cpp
+++ b/layout/generic/nsSubDocumentFrame.cpp
@@ -671,7 +671,7 @@ nsSubDocumentFrame::GetIntrinsicSize()
   return nsAtomicContainerFrame::GetIntrinsicSize();
 }
 
-/* virtual */ nsSize
+/* virtual */ AspectRatio
 nsSubDocumentFrame::GetIntrinsicRatio()
 {
   nsIFrame* subDocRoot = ObtainIntrinsicSizeFrame();
@@ -771,7 +771,7 @@ nsSubDocumentFrame::Reflow(nsPresContext*           aPresContext,
     // Size & position the view according to 'object-fit' & 'object-position'.
     nsIFrame* subDocRoot = ObtainIntrinsicSizeFrame();
     IntrinsicSize intrinsSize;
-    nsSize intrinsRatio;
+    AspectRatio intrinsRatio;
     if (subDocRoot) {
       intrinsSize = subDocRoot->GetIntrinsicSize();
       intrinsRatio = subDocRoot->GetIntrinsicRatio();
diff --git a/layout/generic/nsSubDocumentFrame.h b/layout/generic/nsSubDocumentFrame.h
index 93d908dcc..907d33710 100644
--- a/layout/generic/nsSubDocumentFrame.h
+++ b/layout/generic/nsSubDocumentFrame.h
@@ -51,7 +51,7 @@ public:
   virtual nscoord GetPrefISize(nsRenderingContext *aRenderingContext) override;
 
   virtual mozilla::IntrinsicSize GetIntrinsicSize() override;
-  virtual nsSize  GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
 
   virtual mozilla::LogicalSize
   ComputeAutoSize(nsRenderingContext*         aRenderingContext,
diff --git a/layout/generic/nsVideoFrame.cpp b/layout/generic/nsVideoFrame.cpp
index cea209cb5..0472ebe62 100644
--- a/layout/generic/nsVideoFrame.cpp
+++ b/layout/generic/nsVideoFrame.cpp
@@ -217,12 +217,10 @@ nsVideoFrame::BuildLayer(nsDisplayListBuilder* aBuilder,
   // Convert video size from pixel units into app units, to get an aspect-ratio
   // (which has to be represented as a nsSize) and an IntrinsicSize that we
   // can pass to ComputeObjectRenderRect.
-  nsSize aspectRatio(nsPresContext::CSSPixelsToAppUnits(videoSizeInPx.width),
-                     nsPresContext::CSSPixelsToAppUnits(videoSizeInPx.height));
+  auto aspectRatio = AspectRatio::FromSize(videoSizeInPx);
   IntrinsicSize intrinsicSize;
-  intrinsicSize.width.SetCoordValue(aspectRatio.width);
-  intrinsicSize.height.SetCoordValue(aspectRatio.height);
-
+  intrinsicSize.width.SetCoordValue(nsPresContext::CSSPixelsToAppUnits(videoSizeInPx.width));
+  intrinsicSize.height.SetCoordValue(nsPresContext::CSSPixelsToAppUnits(videoSizeInPx.height));
   nsRect dest = nsLayoutUtils::ComputeObjectDestRect(area,
                                                      intrinsicSize,
                                                      aspectRatio,
@@ -533,7 +531,9 @@ nsVideoFrame::ComputeSize(nsRenderingContext *aRenderingContext,
   intrinsicSize.height.SetCoordValue(size.height);
 
   // Only video elements have an intrinsic ratio.
-  nsSize intrinsicRatio = HasVideoElement() ? size : nsSize(0, 0);
+  auto intrinsicRatio = HasVideoElement() ?
+                        AspectRatio::FromSize(size) :
+                        AspectRatio();
 
   return ComputeSizeWithIntrinsicDimensions(aRenderingContext, aWM,
                                             intrinsicSize, intrinsicRatio,
@@ -557,14 +557,14 @@ nscoord nsVideoFrame::GetPrefISize(nsRenderingContext *aRenderingContext)
   return result;
 }
 
-nsSize nsVideoFrame::GetIntrinsicRatio()
+AspectRatio nsVideoFrame::GetIntrinsicRatio()
 {
   if (!HasVideoElement()) {
     // Audio elements have no intrinsic ratio.
-    return nsSize(0, 0);
+    return AspectRatio();
   }
 
-  return GetVideoIntrinsicSize(nullptr);
+  return AspectRatio::FromSize(GetVideoIntrinsicSize(nullptr));
 }
 
 bool nsVideoFrame::ShouldDisplayPoster()
diff --git a/layout/generic/nsVideoFrame.h b/layout/generic/nsVideoFrame.h
index d624ae6b9..f52cd8277 100644
--- a/layout/generic/nsVideoFrame.h
+++ b/layout/generic/nsVideoFrame.h
@@ -56,7 +56,7 @@ public:
 
   /* get the size of the video's display */
   nsSize GetVideoIntrinsicSize(nsRenderingContext *aRenderingContext);
-  virtual nsSize GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
   virtual mozilla::LogicalSize
   ComputeSize(nsRenderingContext *aRenderingContext,
               mozilla::WritingMode aWritingMode,
diff --git a/layout/style/nsCSSPropAliasList.h b/layout/style/nsCSSPropAliasList.h
index f7938af9e..9ec71b2cf 100644
--- a/layout/style/nsCSSPropAliasList.h
+++ b/layout/style/nsCSSPropAliasList.h
@@ -264,6 +264,11 @@ CSS_PROP_ALIAS(-webkit-animation-timing-function,
                WebkitAnimationTimingFunction,
                WEBKIT_PREFIX_PREF)
 
+CSS_PROP_ALIAS(-webkit-appearance,
+               appearance,
+               WebkitAppearance,
+               WEBKIT_PREFIX_PREF)
+
 CSS_PROP_ALIAS(-webkit-filter,
                filter,
                WebkitFilter,
diff --git a/layout/style/nsCSSPropList.h b/layout/style/nsCSSPropList.h
index 411f982a4..44bd44cef 100644
--- a/layout/style/nsCSSPropList.h
+++ b/layout/style/nsCSSPropList.h
@@ -470,6 +470,17 @@ CSS_PROP_DISPLAY(
     kAppearanceKTable,
     CSS_PROP_NO_OFFSET,
     eStyleAnimType_Discrete)
+CSS_PROP_POSITION(
+    aspect-ratio,
+    aspect_ratio,
+    AspectRatio,
+    CSS_PROPERTY_INTERNAL |
+        CSS_PROPERTY_PARSE_INACCESSIBLE,
+    "",
+    VARIANT_NUMBER,
+    nullptr,
+    offsetof(nsStylePosition, mAspectRatio),
+    eStyleAnimType_None)
 CSS_PROP_DISPLAY(
     backface-visibility,
     backface_visibility,
diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index a0f65c069..1a451a2ef 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -8544,6 +8544,12 @@ nsRuleNode::ComputePositionData(void* aStartStruct,
              SETCOORD_UNSET_INITIAL,
            aContext, mPresContext, conditions);
 
+  // aspect-ratio: float, initial
+  SetFactor(*aRuleData->ValueForAspectRatio(),
+           pos->mAspectRatio, conditions,
+           parentPos->mAspectRatio, 0.0f,
+           SETFCT_UNSET_INITIAL | SETFCT_POSITIVE | SETFCT_NONE);
+
   // box-sizing: enum, inherit, initial
   SetValue(*aRuleData->ValueForBoxSizing(),
            pos->mBoxSizing, conditions,
diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index 200f934c5..3b19a4418 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -1408,6 +1408,7 @@ nsStylePosition::nsStylePosition(StyleStructContext aContext)
   , mGridAutoColumnsMax(eStyleUnit_Auto)
   , mGridAutoRowsMin(eStyleUnit_Auto)
   , mGridAutoRowsMax(eStyleUnit_Auto)
+  , mAspectRatio(0.0f)
   , mGridAutoFlow(NS_STYLE_GRID_AUTO_FLOW_ROW)
   , mBoxSizing(StyleBoxSizing::Content)
   , mAlignContent(NS_STYLE_ALIGN_NORMAL)
@@ -1466,6 +1467,7 @@ nsStylePosition::nsStylePosition(const nsStylePosition& aSource)
   , mGridAutoColumnsMax(aSource.mGridAutoColumnsMax)
   , mGridAutoRowsMin(aSource.mGridAutoRowsMin)
   , mGridAutoRowsMax(aSource.mGridAutoRowsMax)
+  , mAspectRatio(aSource.mAspectRatio)
   , mGridAutoFlow(aSource.mGridAutoFlow)
   , mBoxSizing(aSource.mBoxSizing)
   , mAlignContent(aSource.mAlignContent)
@@ -1636,6 +1638,11 @@ nsStylePosition::CalcDifference(const nsStylePosition& aNewData,
     if (isVertical ? heightChanged : widthChanged) {
       hint |= nsChangeHint_ReflowHintsForISizeChange;
     }
+
+    if (mAspectRatio != aNewData.mAspectRatio) {
+      hint |= nsChangeHint_ReflowHintsForISizeChange |
+              nsChangeHint_ReflowHintsForBSizeChange;
+    }
   } else {
     if (widthChanged || heightChanged) {
       hint |= nsChangeHint_NeutralChange;
@@ -2731,7 +2738,7 @@ nsStyleImageLayers::Size::DependsOnPositioningAreaSize(const nsStyleImage& aImag
     }
     if (imgContainer) {
       CSSIntSize imageSize;
-      nsSize imageRatio;
+      AspectRatio imageRatio;
       bool hasWidth, hasHeight;
       nsLayoutUtils::ComputeSizeForDrawing(imgContainer, imageSize, imageRatio,
                                            hasWidth, hasHeight);
@@ -2744,7 +2751,7 @@ nsStyleImageLayers::Size::DependsOnPositioningAreaSize(const nsStyleImage& aImag
 
       // If the image has an intrinsic ratio, rendering will depend on frame
       // size when background-size is all auto.
-      if (imageRatio != nsSize(0, 0)) {
+      if (imageRatio) {
         return mWidthType == mHeightType;
       }
 
diff --git a/layout/style/nsStyleStruct.h b/layout/style/nsStyleStruct.h
index b257c6bb5..4bda817dd 100644
--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -1815,6 +1815,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStylePosition
   nsStyleCoord  mGridAutoColumnsMax;    // [reset] coord, percent, enum, calc, flex
   nsStyleCoord  mGridAutoRowsMin;       // [reset] coord, percent, enum, calc, flex
   nsStyleCoord  mGridAutoRowsMax;       // [reset] coord, percent, enum, calc, flex
+  float         mAspectRatio;           // [reset] float
   uint8_t       mGridAutoFlow;          // [reset] enumerated. See nsStyleConsts.h
   mozilla::StyleBoxSizing mBoxSizing;   // [reset] see nsStyleConsts.h
 
diff --git a/layout/style/test/ListCSSProperties.cpp b/layout/style/test/ListCSSProperties.cpp
index 718032f61..9f727104b 100644
--- a/layout/style/test/ListCSSProperties.cpp
+++ b/layout/style/test/ListCSSProperties.cpp
@@ -106,6 +106,7 @@ const char *gInaccessibleProperties[] = {
     "-x-span",
     "-x-system-font",
     "-x-text-zoom",
+    "aspect-ratio",  // for now.
     "-moz-control-character-visibility",
     "-moz-script-level", // parsed by UA sheets only
     "-moz-script-size-multiplier",
diff --git a/layout/svg/nsSVGOuterSVGFrame.cpp b/layout/svg/nsSVGOuterSVGFrame.cpp
index 16dfc2b37..3f68245e2 100644
--- a/layout/svg/nsSVGOuterSVGFrame.cpp
+++ b/layout/svg/nsSVGOuterSVGFrame.cpp
@@ -232,28 +232,30 @@ nsSVGOuterSVGFrame::GetIntrinsicSize()
   return intrinsicSize;
 }
 
-/* virtual */ nsSize
+/* virtual */ AspectRatio
 nsSVGOuterSVGFrame::GetIntrinsicRatio()
-{
+{ 
+ // When 'contain: size' is implemented, make sure to check for it.
+/*
+  if (this->GetContent->GetParent() && this->StyleDisplay()->IsContainSize()) {
+    return AspectRatio();
+  }
+ */
+
   // We only have an intrinsic size/ratio if our width and height attributes
   // are both specified and set to non-percentage values, or we have a viewBox
   // rect: http://www.w3.org/TR/SVGMobile12/coords.html#IntrinsicSizing
+  // Unfortunately we have to return the ratio as two nscoords whereas what
+  // we have are two floats. Using app units allows for some floating point
+  // values to work but really small or large numbers will fail.
 
   SVGSVGElement *content = static_cast<SVGSVGElement*>(mContent);
   nsSVGLength2 &width  = content->mLengthAttributes[SVGSVGElement::ATTR_WIDTH];
   nsSVGLength2 &height = content->mLengthAttributes[SVGSVGElement::ATTR_HEIGHT];
 
   if (!width.IsPercentage() && !height.IsPercentage()) {
-    nsSize ratio(
-      nsPresContext::CSSPixelsToAppUnits(width.GetAnimValue(content)),
-      nsPresContext::CSSPixelsToAppUnits(height.GetAnimValue(content)));
-    if (ratio.width < 0) {
-      ratio.width = 0;
-    }
-    if (ratio.height < 0) {
-      ratio.height = 0;
-    }
-    return ratio;
+    return AspectRatio::FromSize(width.GetAnimValue(content),
+                                 height.GetAnimValue(content));
   }
 
   SVGViewElement* viewElement = content->GetCurrentViewElement();
@@ -267,17 +269,7 @@ nsSVGOuterSVGFrame::GetIntrinsicRatio()
   }
 
   if (viewbox) {
-    float viewBoxWidth = viewbox->width;
-    float viewBoxHeight = viewbox->height;
-
-    if (viewBoxWidth < 0.0f) {
-      viewBoxWidth = 0.0f;
-    }
-    if (viewBoxHeight < 0.0f) {
-      viewBoxHeight = 0.0f;
-    }
-    return nsSize(nsPresContext::CSSPixelsToAppUnits(viewBoxWidth),
-                  nsPresContext::CSSPixelsToAppUnits(viewBoxHeight));
+    return AspectRatio::FromSize(viewbox->width, viewbox->height);
   }
 
   return nsSVGDisplayContainerFrame::GetIntrinsicRatio();
diff --git a/layout/svg/nsSVGOuterSVGFrame.h b/layout/svg/nsSVGOuterSVGFrame.h
index ee59b7d1c..4705b6ebe 100644
--- a/layout/svg/nsSVGOuterSVGFrame.h
+++ b/layout/svg/nsSVGOuterSVGFrame.h
@@ -42,7 +42,7 @@ public:
   virtual nscoord GetPrefISize(nsRenderingContext *aRenderingContext) override;
 
   virtual mozilla::IntrinsicSize GetIntrinsicSize() override;
-  virtual nsSize  GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
 
   virtual mozilla::LogicalSize
   ComputeSize(nsRenderingContext *aRenderingContext,
diff --git a/layout/xul/nsImageBoxFrame.cpp b/layout/xul/nsImageBoxFrame.cpp
index e88b502ab..aa00c5174 100644
--- a/layout/xul/nsImageBoxFrame.cpp
+++ b/layout/xul/nsImageBoxFrame.cpp
@@ -402,12 +402,12 @@ nsImageBoxFrame::PaintImage(nsRenderingContext& aRenderingContext,
     // Determine dest rect based on intrinsic size & ratio, along with
     // 'object-fit' & 'object-position' properties:
     IntrinsicSize intrinsicSize;
-    nsSize intrinsicRatio;
+    AspectRatio intrinsicRatio;
     if (mIntrinsicSize.width > 0 && mIntrinsicSize.height > 0) {
       // Image has a valid size; use it as intrinsic size & ratio.
       intrinsicSize.width.SetCoordValue(mIntrinsicSize.width);
       intrinsicSize.height.SetCoordValue(mIntrinsicSize.height);
-      intrinsicRatio = mIntrinsicSize;
+      intrinsicRatio = AspectRatio::FromSize(mIntrinsicSize);
     } else {
       // Image doesn't have a (valid) intrinsic size.
       // Try to look up intrinsic ratio and use that at least.