DevTools: extract HeapTimelineOverview into a separate file.

No changes to the class except renaming from HeapTrackingOverviewGrid

BUG=889545

Change-Id: I6ffd4d40e7ca9d34e37794ebcc1a631ad3b40ff9
Reviewed-on: https://chromium-review.googlesource.com/1246362
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594483}

third_party/blink/renderer/devtools/BUILD.gn

@@ -509,11 +509,12 @@ all_devtools_files = [
   "front_end/profiler/CPUProfileView.js",
   "front_end/profiler/heapProfiler.css",
   "front_end/profiler/HeapProfileView.js",
+  "front_end/profiler/HeapProfilerPanel.js",
   "front_end/profiler/HeapSnapshotDataGrids.js",
   "front_end/profiler/HeapSnapshotGridNodes.js",
   "front_end/profiler/HeapSnapshotProxy.js",
   "front_end/profiler/HeapSnapshotView.js",
-  "front_end/profiler/HeapProfilerPanel.js",
+  "front_end/profiler/HeapTimelineOverview.js",
   "front_end/profiler/IsolateSelector.js",
   "front_end/profiler/module.json",
   "front_end/profiler/ProfileDataGrid.js",

third_party/blink/renderer/devtools/front_end/profiler/module.json

@@ -92,11 +92,12 @@
         "CPUProfileFlameChart.js",
         "CPUProfileView.js",
         "HeapProfileView.js",
+        "HeapProfilerPanel.js",
         "HeapSnapshotProxy.js",
         "HeapSnapshotDataGrids.js",
         "HeapSnapshotGridNodes.js",
         "HeapSnapshotView.js",
-        "HeapProfilerPanel.js",
+        "HeapTimelineOverview.js",
         "IsolateSelector.js",
         "ProfileLauncherView.js",
         "ProfileTypeRegistry.js"