DevTools: Add JSDoc for static methods, fix JSDoc types and induced errors

Source/devtools/front_end/timeline/TimelineFlameChart.js

Index: Source/devtools/front_end/timeline/TimelineFlameChart.js
diff --git a/Source/devtools/front_end/timeline/TimelineFlameChart.js b/Source/devtools/front_end/timeline/TimelineFlameChart.js
index 84f52574e371ac0510917f7b16117ecb886673e7..29be2d31641dd31b746e734547901c9e2c36061f 100644
--- a/Source/devtools/front_end/timeline/TimelineFlameChart.js
+++ b/Source/devtools/front_end/timeline/TimelineFlameChart.js
@@ -271,7 +271,7 @@ WebInspector.TimelineFlameChartDataProvider.prototype = {
 
     /**
      * @param {number} entryIndex
-     * @return {!string}
+     * @return {string}
      */
     entryColor: function(entryIndex)
     {
@@ -395,7 +395,7 @@ WebInspector.TimelineFlameChartDataProvider.prototype = {
 
     /**
      * @param {number} entryIndex
-     * @return {!string}
+     * @return {string}
      */
     textColor: function(entryIndex)
     {
@@ -615,7 +615,7 @@ WebInspector.TracingBasedTimelineFlameChartDataProvider.prototype = {
 
     /**
      * @param {number} entryIndex
-     * @return {!string}
+     * @return {string}
      */
     entryColor: function(entryIndex)
     {
@@ -713,7 +713,7 @@ WebInspector.TracingBasedTimelineFlameChartDataProvider.prototype = {
 
     /**
      * @param {number} entryIndex
-     * @return {!string}
+     * @return {string}
      */
     textColor: function(entryIndex)
     {