2 files changed, 30 insertions, 0 deletions
diff --git a/toolkit/components/reader/AboutReader.jsm b/toolkit/components/reader/AboutReader.jsm
index 5defa623e..9d9362a0c 100644
--- a/toolkit/components/reader/AboutReader.jsm
+++ b/toolkit/components/reader/AboutReader.jsm
@@ -120,6 +120,25 @@ var AboutReader = function(win, articlePromise) {
   }
 
   this._loadArticle();
+
+  let dropdown = this._toolbarElement;
+
+  let elemL10nMap = {
+    ".minus-button": "minus",
+    ".plus-button": "plus",
+    ".content-width-minus-button": "contentwidthminus",
+    ".content-width-plus-button": "contentwidthplus",
+    ".line-height-minus-button": "lineheightminus",
+    ".line-height-plus-button": "lineheightplus",
+    ".light-button": "colorschemelight",
+    ".dark-button": "colorschemedark",
+    ".sepia-button": "colorschemesepia",
+  };
+
+  for (let [selector, stringID] of Object.entries(elemL10nMap)) {
+    dropdown.querySelector(selector).setAttribute("title",
+      gStrings.GetStringFromName("aboutReader.toolbar." + stringID));
+  }
 };
 
 AboutReader.prototype = {
diff --git a/toolkit/locales/en-US/chrome/global/aboutReader.properties b/toolkit/locales/en-US/chrome/global/aboutReader.properties
index ac004c545..10d145686 100644
--- a/toolkit/locales/en-US/chrome/global/aboutReader.properties
+++ b/toolkit/locales/en-US/chrome/global/aboutReader.properties
@@ -46,3 +46,14 @@ readerView.enter=Enter Reader View
 readerView.enter.accesskey=R
 readerView.close=Close Reader View
 readerView.close.accesskey=R
+
+# These are used as tooltips in Type Control
+aboutReader.toolbar.minus = Decrease Font Size
+aboutReader.toolbar.plus = Increase Font Size
+aboutReader.toolbar.contentwidthminus = Decrease Content Width
+aboutReader.toolbar.contentwidthplus = Increase Content Width
+aboutReader.toolbar.lineheightminus = Decrease Line Height
+aboutReader.toolbar.lineheightplus = Increase Line Height
+aboutReader.toolbar.colorschemelight = Color Scheme Light
+aboutReader.toolbar.colorschemedark = Color Scheme Dark
+aboutReader.toolbar.colorschemesepia = Color Scheme Sepia