12 files changed, 895 insertions, 0 deletions
diff --git a/devtools/client/memory/reducers/allocations.js b/devtools/client/memory/reducers/allocations.js
new file mode 100644
index 000000000..ccb92f825
--- /dev/null
+++ b/devtools/client/memory/reducers/allocations.js
@@ -0,0 +1,42 @@
+/* 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/. */
+
+const { assert } = require("devtools/shared/DevToolsUtils");
+const { actions } = require("../constants");
+
+let handlers = Object.create(null);
+
+handlers[actions.TOGGLE_RECORD_ALLOCATION_STACKS_START] = function (state, action) {
+  assert(!state.togglingInProgress,
+         "Changing recording state must not be reentrant.");
+
+  return {
+    recording: !state.recording,
+    togglingInProgress: true,
+  };
+};
+
+handlers[actions.TOGGLE_RECORD_ALLOCATION_STACKS_END] = function (state, action) {
+  assert(state.togglingInProgress,
+         "Should not complete changing recording state if we weren't changing "
+         + "recording state already.");
+
+  return {
+    recording: state.recording,
+    togglingInProgress: false,
+  };
+};
+
+const DEFAULT_ALLOCATIONS_STATE = {
+  recording: false,
+  togglingInProgress: false
+};
+
+module.exports = function (state = DEFAULT_ALLOCATIONS_STATE, action) {
+  let handle = handlers[action.type];
+  if (handle) {
+    return handle(state, action);
+  }
+  return state;
+};
diff --git a/devtools/client/memory/reducers/census-display.js b/devtools/client/memory/reducers/census-display.js
new file mode 100644
index 000000000..83535a201
--- /dev/null
+++ b/devtools/client/memory/reducers/census-display.js
@@ -0,0 +1,21 @@
+/* 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/. */
+"use strict";
+
+const { actions, censusDisplays } = require("../constants");
+const DEFAULT_CENSUS_DISPLAY = censusDisplays.coarseType;
+
+let handlers = Object.create(null);
+
+handlers[actions.SET_CENSUS_DISPLAY] = function (_, { display }) {
+  return display;
+};
+
+module.exports = function (state = DEFAULT_CENSUS_DISPLAY, action) {
+  let handle = handlers[action.type];
+  if (handle) {
+    return handle(state, action);
+  }
+  return state;
+};
diff --git a/devtools/client/memory/reducers/diffing.js b/devtools/client/memory/reducers/diffing.js
new file mode 100644
index 000000000..6d4973c8e
--- /dev/null
+++ b/devtools/client/memory/reducers/diffing.js
@@ -0,0 +1,146 @@
+/* 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/. */
+"use strict";
+
+const Immutable = require("devtools/client/shared/vendor/immutable");
+const { immutableUpdate, assert } = require("devtools/shared/DevToolsUtils");
+const { actions, diffingState, viewState } = require("../constants");
+const { snapshotIsDiffable } = require("../utils");
+
+const handlers = Object.create(null);
+
+handlers[actions.POP_VIEW] = function (diffing, { previousView }) {
+  if (previousView.state === viewState.DIFFING) {
+    assert(previousView.diffing, "Should have previousView.diffing");
+    return previousView.diffing;
+  }
+
+  return null;
+};
+
+handlers[actions.CHANGE_VIEW] = function (diffing, { newViewState }) {
+  if (newViewState === viewState.DIFFING) {
+    assert(!diffing, "Should not switch to diffing view when already diffing");
+    return Object.freeze({
+      firstSnapshotId: null,
+      secondSnapshotId: null,
+      census: null,
+      state: diffingState.SELECTING,
+    });
+  }
+
+  return null;
+};
+
+handlers[actions.SELECT_SNAPSHOT_FOR_DIFFING] = function (diffing, { snapshot }) {
+  assert(diffing,
+         "Should never select a snapshot for diffing when we aren't diffing " +
+         "anything");
+  assert(diffing.state === diffingState.SELECTING,
+         "Can't select when not in SELECTING state");
+  assert(snapshotIsDiffable(snapshot),
+         "snapshot must be in a diffable state");
+
+  if (!diffing.firstSnapshotId) {
+    return immutableUpdate(diffing, {
+      firstSnapshotId: snapshot.id
+    });
+  }
+
+  assert(!diffing.secondSnapshotId,
+         "If we aren't selecting the first, then we must be selecting the " +
+         "second");
+
+  if (snapshot.id === diffing.firstSnapshotId) {
+    // Ignore requests to select the same snapshot.
+    return diffing;
+  }
+
+  return immutableUpdate(diffing, {
+    secondSnapshotId: snapshot.id
+  });
+};
+
+handlers[actions.TAKE_CENSUS_DIFF_START] = function (diffing, action) {
+  assert(diffing, "Should be diffing when starting a census diff");
+  assert(action.first.id === diffing.firstSnapshotId,
+         "First snapshot's id should match");
+  assert(action.second.id === diffing.secondSnapshotId,
+         "Second snapshot's id should match");
+
+  return immutableUpdate(diffing, {
+    state: diffingState.TAKING_DIFF,
+    census: {
+      report: null,
+      inverted: action.inverted,
+      filter: action.filter,
+      display: action.display,
+    }
+  });
+};
+
+handlers[actions.TAKE_CENSUS_DIFF_END] = function (diffing, action) {
+  assert(diffing, "Should be diffing when ending a census diff");
+  assert(action.first.id === diffing.firstSnapshotId,
+         "First snapshot's id should match");
+  assert(action.second.id === diffing.secondSnapshotId,
+         "Second snapshot's id should match");
+
+  return immutableUpdate(diffing, {
+    state: diffingState.TOOK_DIFF,
+    census: {
+      report: action.report,
+      parentMap: action.parentMap,
+      expanded: Immutable.Set(),
+      inverted: action.inverted,
+      filter: action.filter,
+      display: action.display,
+    }
+  });
+};
+
+handlers[actions.DIFFING_ERROR] = function (diffing, action) {
+  return {
+    state: diffingState.ERROR,
+    error: action.error
+  };
+};
+
+handlers[actions.EXPAND_DIFFING_CENSUS_NODE] = function (diffing, { node }) {
+  assert(diffing, "Should be diffing if expanding diffing's census nodes");
+  assert(diffing.state === diffingState.TOOK_DIFF,
+         "Should have taken the census diff if expanding nodes");
+  assert(diffing.census, "Should have a census");
+  assert(diffing.census.report, "Should have a census report");
+  assert(diffing.census.expanded, "Should have a census's expanded set");
+
+  const expanded = diffing.census.expanded.add(node.id);
+  const census = immutableUpdate(diffing.census, { expanded });
+  return immutableUpdate(diffing, { census });
+};
+
+handlers[actions.COLLAPSE_DIFFING_CENSUS_NODE] = function (diffing, { node }) {
+  assert(diffing, "Should be diffing if expanding diffing's census nodes");
+  assert(diffing.state === diffingState.TOOK_DIFF,
+         "Should have taken the census diff if expanding nodes");
+  assert(diffing.census, "Should have a census");
+  assert(diffing.census.report, "Should have a census report");
+  assert(diffing.census.expanded, "Should have a census's expanded set");
+
+  const expanded = diffing.census.expanded.delete(node.id);
+  const census = immutableUpdate(diffing.census, { expanded });
+  return immutableUpdate(diffing, { census });
+};
+
+handlers[actions.FOCUS_DIFFING_CENSUS_NODE] = function (diffing, { node }) {
+  assert(diffing, "Should be diffing.");
+  assert(diffing.census, "Should have a census");
+  const census = immutableUpdate(diffing.census, { focused: node });
+  return immutableUpdate(diffing, { census });
+};
+
+module.exports = function (diffing = null, action) {
+  const handler = handlers[action.type];
+  return handler ? handler(diffing, action) : diffing;
+};
diff --git a/devtools/client/memory/reducers/errors.js b/devtools/client/memory/reducers/errors.js
new file mode 100644
index 000000000..5fc282df2
--- /dev/null
+++ b/devtools/client/memory/reducers/errors.js
@@ -0,0 +1,17 @@
+/* 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/. */
+
+const { ERROR_TYPE: TASK_ERROR_TYPE } = require("devtools/client/shared/redux/middleware/task");
+
+/**
+ * Handle errors dispatched from task middleware and
+ * store them so we can check in tests or dump them out.
+ */
+module.exports = function (state = [], action) {
+  switch (action.type) {
+    case TASK_ERROR_TYPE:
+      return [...state, action.error];
+  }
+  return state;
+};
diff --git a/devtools/client/memory/reducers/filter.js b/devtools/client/memory/reducers/filter.js
new file mode 100644
index 000000000..99188142c
--- /dev/null
+++ b/devtools/client/memory/reducers/filter.js
@@ -0,0 +1,14 @@
+/* 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/. */
+"use strict";
+
+const { actions } = require("../constants");
+
+module.exports = function (filterString = null, action) {
+  if (action.type === actions.SET_FILTER_STRING) {
+    return action.filter || null;
+  } else {
+    return filterString;
+  }
+};
diff --git a/devtools/client/memory/reducers/individuals.js b/devtools/client/memory/reducers/individuals.js
new file mode 100644
index 000000000..10f016fe5
--- /dev/null
+++ b/devtools/client/memory/reducers/individuals.js
@@ -0,0 +1,73 @@
+/* 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/. */
+"use strict";
+
+const { assert, immutableUpdate } = require("devtools/shared/DevToolsUtils");
+const { actions, individualsState, viewState } = require("../constants");
+
+const handlers = Object.create(null);
+
+handlers[actions.POP_VIEW] = function (_state, _action) {
+  return null;
+};
+
+handlers[actions.CHANGE_VIEW] = function (individuals, { newViewState }) {
+  if (newViewState === viewState.INDIVIDUALS) {
+    assert(!individuals,
+           "Should not switch to individuals view when already in individuals view");
+    return Object.freeze({
+      state: individualsState.COMPUTING_DOMINATOR_TREE,
+    });
+  }
+
+  return null;
+};
+
+handlers[actions.FOCUS_INDIVIDUAL] = function (individuals, { node }) {
+  assert(individuals, "Should have individuals");
+  return immutableUpdate(individuals, { focused: node });
+};
+
+handlers[actions.FETCH_INDIVIDUALS_START] = function (individuals, action) {
+  assert(individuals, "Should have individuals");
+  return Object.freeze({
+    state: individualsState.FETCHING,
+    focused: individuals.focused,
+  });
+};
+
+handlers[actions.FETCH_INDIVIDUALS_END] = function (individuals, action) {
+  assert(individuals, "Should have individuals");
+  assert(!individuals.nodes, "Should not have nodes");
+  assert(individuals.state === individualsState.FETCHING,
+         "Should only end fetching individuals after starting.");
+
+  const focused = individuals.focused
+    ? action.nodes.find(n => n.nodeId === individuals.focused.nodeId)
+    : null;
+
+  return Object.freeze({
+    state: individualsState.FETCHED,
+    nodes: action.nodes,
+    id: action.id,
+    censusBreakdown: action.censusBreakdown,
+    indices: action.indices,
+    labelDisplay: action.labelDisplay,
+    focused,
+    dominatorTree: action.dominatorTree,
+  });
+};
+
+handlers[actions.INDIVIDUALS_ERROR] = function (_, { error }) {
+  return Object.freeze({
+    error,
+    nodes: null,
+    state: individualsState.ERROR,
+  });
+};
+
+module.exports = function (individuals = null, action) {
+  const handler = handlers[action.type];
+  return handler ? handler(individuals, action) : individuals;
+};
diff --git a/devtools/client/memory/reducers/label-display.js b/devtools/client/memory/reducers/label-display.js
new file mode 100644
index 000000000..e7d142682
--- /dev/null
+++ b/devtools/client/memory/reducers/label-display.js
@@ -0,0 +1,19 @@
+/* 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/. */
+
+"use strict";
+
+const { actions, labelDisplays } = require("../constants");
+const DEFAULT_LABEL_DISPLAY = labelDisplays.coarseType;
+
+const handlers = Object.create(null);
+
+handlers[actions.SET_LABEL_DISPLAY] = function (_, { display }) {
+  return display;
+};
+
+module.exports = function (state = DEFAULT_LABEL_DISPLAY, action) {
+  const handler = handlers[action.type];
+  return handler ? handler(state, action) : state;
+};
diff --git a/devtools/client/memory/reducers/moz.build b/devtools/client/memory/reducers/moz.build
new file mode 100644
index 000000000..664c4496c
--- /dev/null
+++ b/devtools/client/memory/reducers/moz.build
@@ -0,0 +1,18 @@
+# vim: set filetype=python:
+# 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/.
+
+DevToolsModules(
+    'allocations.js',
+    'census-display.js',
+    'diffing.js',
+    'errors.js',
+    'filter.js',
+    'individuals.js',
+    'label-display.js',
+    'sizes.js',
+    'snapshots.js',
+    'tree-map-display.js',
+    'view.js',
+)
diff --git a/devtools/client/memory/reducers/sizes.js b/devtools/client/memory/reducers/sizes.js
new file mode 100644
index 000000000..f04530cfc
--- /dev/null
+++ b/devtools/client/memory/reducers/sizes.js
@@ -0,0 +1,18 @@
+/* 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/. */
+"use strict";
+
+const { actions } = require("../constants");
+const { immutableUpdate } = require("devtools/shared/DevToolsUtils");
+
+const handlers = Object.create(null);
+
+handlers[actions.RESIZE_SHORTEST_PATHS] = function (sizes, { size }) {
+  return immutableUpdate(sizes, { shortestPathsSize: size });
+};
+
+module.exports = function (sizes = { shortestPathsSize: .5 }, action) {
+  const handler = handlers[action.type];
+  return handler ? handler(sizes, action) : sizes;
+};
diff --git a/devtools/client/memory/reducers/snapshots.js b/devtools/client/memory/reducers/snapshots.js
new file mode 100644
index 000000000..6293bdded
--- /dev/null
+++ b/devtools/client/memory/reducers/snapshots.js
@@ -0,0 +1,459 @@
+/* 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/. */
+"use strict";
+
+const Immutable = require("devtools/client/shared/vendor/immutable");
+const { immutableUpdate, assert } = require("devtools/shared/DevToolsUtils");
+const {
+  actions,
+  snapshotState: states,
+  censusState,
+  treeMapState,
+  dominatorTreeState,
+  viewState,
+} = require("../constants");
+const DominatorTreeNode = require("devtools/shared/heapsnapshot/DominatorTreeNode");
+
+const handlers = Object.create(null);
+
+handlers[actions.SNAPSHOT_ERROR] = function (snapshots, { id, error }) {
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { state: states.ERROR, error })
+      : snapshot;
+  });
+};
+
+handlers[actions.TAKE_SNAPSHOT_START] = function (snapshots, { snapshot }) {
+  return [...snapshots, snapshot];
+};
+
+handlers[actions.TAKE_SNAPSHOT_END] = function (snapshots, { id, path }) {
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { state: states.SAVED, path })
+      : snapshot;
+  });
+};
+
+handlers[actions.IMPORT_SNAPSHOT_START] = handlers[actions.TAKE_SNAPSHOT_START];
+
+handlers[actions.READ_SNAPSHOT_START] = function (snapshots, { id }) {
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { state: states.READING })
+      : snapshot;
+  });
+};
+
+handlers[actions.READ_SNAPSHOT_END] = function (snapshots, { id, creationTime }) {
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { state: states.READ, creationTime })
+      : snapshot;
+  });
+};
+
+handlers[actions.TAKE_CENSUS_START] = function (snapshots, { id, display, filter }) {
+  const census = {
+    report: null,
+    display,
+    filter,
+    state: censusState.SAVING
+  };
+
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { census })
+      : snapshot;
+  });
+};
+
+handlers[actions.TAKE_CENSUS_END] = function (snapshots, { id,
+                                                           report,
+                                                           parentMap,
+                                                           display,
+                                                           filter }) {
+  const census = {
+    report,
+    parentMap,
+    expanded: Immutable.Set(),
+    display,
+    filter,
+    state: censusState.SAVED
+  };
+
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { census })
+      : snapshot;
+  });
+};
+
+handlers[actions.TAKE_CENSUS_ERROR] = function (snapshots, { id, error }) {
+  assert(error, "actions with TAKE_CENSUS_ERROR should have an error");
+
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    const census = Object.freeze({
+      state: censusState.ERROR,
+      error,
+    });
+
+    return immutableUpdate(snapshot, { census });
+  });
+};
+
+handlers[actions.TAKE_TREE_MAP_START] = function (snapshots, { id, display }) {
+  const treeMap = {
+    report: null,
+    display,
+    state: treeMapState.SAVING
+  };
+
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { treeMap })
+      : snapshot;
+  });
+};
+
+handlers[actions.TAKE_TREE_MAP_END] = function (snapshots, action) {
+  const { id, report, display } = action;
+  const treeMap = {
+    report,
+    display,
+    state: treeMapState.SAVED
+  };
+
+  return snapshots.map(snapshot => {
+    return snapshot.id === id
+      ? immutableUpdate(snapshot, { treeMap })
+      : snapshot;
+  });
+};
+
+handlers[actions.TAKE_TREE_MAP_ERROR] = function (snapshots, { id, error }) {
+  assert(error, "actions with TAKE_TREE_MAP_ERROR should have an error");
+
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    const treeMap = Object.freeze({
+      state: treeMapState.ERROR,
+      error,
+    });
+
+    return immutableUpdate(snapshot, { treeMap });
+  });
+};
+
+handlers[actions.EXPAND_CENSUS_NODE] = function (snapshots, { id, node }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.census, "Should have a census");
+    assert(snapshot.census.report, "Should have a census report");
+    assert(snapshot.census.expanded, "Should have a census's expanded set");
+
+    const expanded = snapshot.census.expanded.add(node.id);
+    const census = immutableUpdate(snapshot.census, { expanded });
+    return immutableUpdate(snapshot, { census });
+  });
+};
+
+handlers[actions.COLLAPSE_CENSUS_NODE] = function (snapshots, { id, node }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.census, "Should have a census");
+    assert(snapshot.census.report, "Should have a census report");
+    assert(snapshot.census.expanded, "Should have a census's expanded set");
+
+    const expanded = snapshot.census.expanded.delete(node.id);
+    const census = immutableUpdate(snapshot.census, { expanded });
+    return immutableUpdate(snapshot, { census });
+  });
+};
+
+handlers[actions.FOCUS_CENSUS_NODE] = function (snapshots, { id, node }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.census, "Should have a census");
+    const census = immutableUpdate(snapshot.census, { focused: node });
+    return immutableUpdate(snapshot, { census });
+  });
+};
+
+handlers[actions.SELECT_SNAPSHOT] = function (snapshots, { id }) {
+  return snapshots.map(s => immutableUpdate(s, { selected: s.id === id }));
+};
+
+handlers[actions.DELETE_SNAPSHOTS_START] = function (snapshots, { ids }) {
+  return snapshots.filter(s => ids.indexOf(s.id) === -1);
+};
+
+handlers[actions.DELETE_SNAPSHOTS_END] = function (snapshots) {
+  return snapshots;
+};
+
+handlers[actions.CHANGE_VIEW] = function (snapshots, { newViewState }) {
+  return newViewState === viewState.DIFFING
+    ? snapshots.map(s => immutableUpdate(s, { selected: false }))
+    : snapshots;
+};
+
+handlers[actions.POP_VIEW] = function (snapshots, { previousView }) {
+  return snapshots.map(s => immutableUpdate(s, {
+    selected: s.id === previousView.selected
+  }));
+};
+
+handlers[actions.COMPUTE_DOMINATOR_TREE_START] = function (snapshots, { id }) {
+  const dominatorTree = Object.freeze({
+    state: dominatorTreeState.COMPUTING,
+    dominatorTreeId: undefined,
+    root: undefined,
+  });
+
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(!snapshot.dominatorTree,
+           "Should not have a dominator tree model");
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.COMPUTE_DOMINATOR_TREE_END] = function (snapshots, { id, dominatorTreeId }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree model");
+    assert(snapshot.dominatorTree.state == dominatorTreeState.COMPUTING,
+           "Should be in the COMPUTING state");
+
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, {
+      state: dominatorTreeState.COMPUTED,
+      dominatorTreeId,
+    });
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.FETCH_DOMINATOR_TREE_START] = function (snapshots, { id, display }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree model");
+    assert(snapshot.dominatorTree.state !== dominatorTreeState.COMPUTING &&
+           snapshot.dominatorTree.state !== dominatorTreeState.ERROR,
+           `Should have already computed the dominator tree, found state = ${snapshot.dominatorTree.state}`);
+
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, {
+      state: dominatorTreeState.FETCHING,
+      root: undefined,
+      display,
+    });
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.FETCH_DOMINATOR_TREE_END] = function (snapshots, { id, root }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree model");
+    assert(snapshot.dominatorTree.state == dominatorTreeState.FETCHING,
+           "Should be in the FETCHING state");
+
+    let focused;
+    if (snapshot.dominatorTree.focused) {
+      focused = (function findFocused(node) {
+        if (node.nodeId === snapshot.dominatorTree.focused.nodeId) {
+          return node;
+        }
+
+        if (node.children) {
+          const length = node.children.length;
+          for (let i = 0; i < length; i++) {
+            const result = findFocused(node.children[i]);
+            if (result) {
+              return result;
+            }
+          }
+        }
+
+        return undefined;
+      }(root));
+    }
+
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, {
+      state: dominatorTreeState.LOADED,
+      root,
+      expanded: Immutable.Set(),
+      focused,
+    });
+
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.EXPAND_DOMINATOR_TREE_NODE] = function (snapshots, { id, node }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree");
+    assert(snapshot.dominatorTree.expanded,
+           "Should have the dominator tree's expanded set");
+
+    const expanded = snapshot.dominatorTree.expanded.add(node.nodeId);
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, { expanded });
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.COLLAPSE_DOMINATOR_TREE_NODE] = function (snapshots, { id, node }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree");
+    assert(snapshot.dominatorTree.expanded,
+           "Should have the dominator tree's expanded set");
+
+    const expanded = snapshot.dominatorTree.expanded.delete(node.nodeId);
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, { expanded });
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.FOCUS_DOMINATOR_TREE_NODE] = function (snapshots, { id, node }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree");
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, { focused: node });
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.FETCH_IMMEDIATELY_DOMINATED_START] = function (snapshots, { id }) {
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    assert(snapshot.dominatorTree, "Should have a dominator tree model");
+    assert(snapshot.dominatorTree.state == dominatorTreeState.INCREMENTAL_FETCHING ||
+           snapshot.dominatorTree.state == dominatorTreeState.LOADED,
+           "The dominator tree should be loaded if we are going to " +
+           "incrementally fetch children.");
+
+    const activeFetchRequestCount = snapshot.dominatorTree.activeFetchRequestCount
+      ? snapshot.dominatorTree.activeFetchRequestCount + 1
+      : 1;
+
+    const dominatorTree = immutableUpdate(snapshot.dominatorTree, {
+      state: dominatorTreeState.INCREMENTAL_FETCHING,
+      activeFetchRequestCount,
+    });
+
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+handlers[actions.FETCH_IMMEDIATELY_DOMINATED_END] =
+  function (snapshots, { id, path, nodes, moreChildrenAvailable}) {
+    return snapshots.map(snapshot => {
+      if (snapshot.id !== id) {
+        return snapshot;
+      }
+
+      assert(snapshot.dominatorTree, "Should have a dominator tree model");
+      assert(snapshot.dominatorTree.root, "Should have a dominator tree model root");
+      assert(snapshot.dominatorTree.state === dominatorTreeState.INCREMENTAL_FETCHING,
+             "The dominator tree state should be INCREMENTAL_FETCHING");
+
+      const root = DominatorTreeNode.insert(snapshot.dominatorTree.root,
+                                            path,
+                                            nodes,
+                                            moreChildrenAvailable);
+
+      const focused = snapshot.dominatorTree.focused
+        ? DominatorTreeNode.getNodeByIdAlongPath(snapshot.dominatorTree.focused.nodeId,
+                                                 root,
+                                                 path)
+        : undefined;
+
+      const activeFetchRequestCount = snapshot.dominatorTree.activeFetchRequestCount === 1
+        ? undefined
+        : snapshot.dominatorTree.activeFetchRequestCount - 1;
+
+      // If there are still outstanding requests, we need to stay in the
+      // INCREMENTAL_FETCHING state until they complete.
+      const state = activeFetchRequestCount
+        ? dominatorTreeState.INCREMENTAL_FETCHING
+        : dominatorTreeState.LOADED;
+
+      const dominatorTree = immutableUpdate(snapshot.dominatorTree, {
+        state,
+        root,
+        focused,
+        activeFetchRequestCount,
+      });
+
+      return immutableUpdate(snapshot, { dominatorTree });
+    });
+  };
+
+handlers[actions.DOMINATOR_TREE_ERROR] = function (snapshots, { id, error }) {
+  assert(error, "actions with DOMINATOR_TREE_ERROR should have an error");
+
+  return snapshots.map(snapshot => {
+    if (snapshot.id !== id) {
+      return snapshot;
+    }
+
+    const dominatorTree = Object.freeze({
+      state: dominatorTreeState.ERROR,
+      error,
+    });
+
+    return immutableUpdate(snapshot, { dominatorTree });
+  });
+};
+
+module.exports = function (snapshots = [], action) {
+  const handler = handlers[action.type];
+  if (handler) {
+    return handler(snapshots, action);
+  }
+  return snapshots;
+};
diff --git a/devtools/client/memory/reducers/tree-map-display.js b/devtools/client/memory/reducers/tree-map-display.js
new file mode 100644
index 000000000..a0d2faadc
--- /dev/null
+++ b/devtools/client/memory/reducers/tree-map-display.js
@@ -0,0 +1,19 @@
+/* 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/. */
+
+"use strict";
+
+const { actions, treeMapDisplays } = require("../constants");
+const DEFAULT_TREE_MAP_DISPLAY = treeMapDisplays.coarseType;
+
+const handlers = Object.create(null);
+
+handlers[actions.SET_TREE_MAP_DISPLAY] = function (_, { display }) {
+  return display;
+};
+
+module.exports = function (state = DEFAULT_TREE_MAP_DISPLAY, action) {
+  const handler = handlers[action.type];
+  return handler ? handler(state, action) : state;
+};
diff --git a/devtools/client/memory/reducers/view.js b/devtools/client/memory/reducers/view.js
new file mode 100644
index 000000000..5d31e0c9b
--- /dev/null
+++ b/devtools/client/memory/reducers/view.js
@@ -0,0 +1,49 @@
+/* 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/. */
+"use strict";
+
+const { assert } = require("devtools/shared/DevToolsUtils");
+const { actions, viewState } = require("../constants");
+
+const handlers = Object.create(null);
+
+handlers[actions.POP_VIEW] = function (view, _) {
+  assert(view.previous, "Had better have a previous view state when POP_VIEW");
+  return Object.freeze({
+    state: view.previous.state,
+    previous: null,
+  });
+};
+
+handlers[actions.CHANGE_VIEW] = function (view, action) {
+  const { newViewState, oldDiffing, oldSelected } = action;
+  assert(newViewState);
+
+  if (newViewState === viewState.INDIVIDUALS) {
+    assert(oldDiffing || oldSelected);
+    return Object.freeze({
+      state: newViewState,
+      previous: Object.freeze({
+        state: view.state,
+        selected: oldSelected,
+        diffing: oldDiffing,
+      }),
+    });
+  }
+
+  return Object.freeze({
+    state: newViewState,
+    previous: null,
+  });
+};
+
+const DEFAULT_VIEW = {
+  state: viewState.TREE_MAP,
+  previous: null,
+};
+
+module.exports = function (view = DEFAULT_VIEW, action) {
+  const handler = handlers[action.type];
+  return handler ? handler(view, action) : view;
+};