FlameChart: convert colors magic into dataProvider.entryColor getter

Source/devtools/front_end/TimelineFlameChart.js

Index: Source/devtools/front_end/TimelineFlameChart.js
diff --git a/Source/devtools/front_end/TimelineFlameChart.js b/Source/devtools/front_end/TimelineFlameChart.js
index cd7e675d4e2fe8418132dd003b976519ee86cbcb..58078b22a1446fb0db38038b1bad363aa91766f0 100644
--- a/Source/devtools/front_end/TimelineFlameChart.js
+++ b/Source/devtools/front_end/TimelineFlameChart.js
@@ -164,12 +164,16 @@ WebInspector.TimelineFlameChartDataProvider.prototype = {
         this._zeroTime = 0;
 
         this._timelineData = {
-            entryLevels: [],
-            entryTotalTimes: [],
-            entryOffsets: [],
-            colorEntryIndexes: []
+            entryLevels: /** @type {!Array.<number>} */ ([]),
+            entryTotalTimes: /** @type {!Array.<number>} */ ([]),
+            entryOffsets: /** @type {!Array.<number>} */ ([]),
         };
-        this._entryTitles = [];
+
+        /** @type {!Array.<string>} */
+        this._entryTitles =  [];
+
+        /** @type {!Array.<string>} */
+        this._entryColors = [];
     },
 
     _appendRecord: function(record, depth)
@@ -195,13 +199,7 @@ WebInspector.TimelineFlameChartDataProvider.prototype = {
         timelineData.entryOffsets[index] = record.startTime - startTime;
         timelineData.entryLevels[index] = depth - 1;
         timelineData.entryTotalTimes[index] = endTime - record.startTime;
-
-        var color = this._colorGenerator.colorForID(WebInspector.TimelineUIUtils.categoryForRecord(record).name);
-        var indexesForColor = timelineData.colorEntryIndexes[color.index];
-        if (!indexesForColor)
-            indexesForColor = timelineData.colorEntryIndexes[color.index] = [];
-        indexesForColor.push(index);
-
+        this._entryColors[index] = this._colorGenerator.colorForID(WebInspector.TimelineUIUtils.categoryForRecord(record).name);
         this._maxStackDepth = Math.max(this._maxStackDepth, depth + 1);
     },
 
@@ -230,6 +228,15 @@ WebInspector.TimelineFlameChartDataProvider.prototype = {
     entryData: function(entryIndex)
     {
         return null;
+    },
+
+    /**
+     * @param {number} entryIndex
+     * @return {!string}
+     */
+    entryColor: function(entryIndex)
+    {
+        return this._entryColors[entryIndex];
     }
 }