[DevTools] Add power profiler and power overview in timeline panel.

Source/devtools/front_end/timelinePanel.css

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 247 matching lines @@
 .timeline-tree-item.selected .data.dimmed {
     color: rgba(255, 255, 255, 0.8);
     pointer-events: auto;
 }
 
 .timeline-tree-item.selected .timeline-tree-item-expand-arrow {
     background-color: white;
 }
 
 #timeline-overview-events,
-#timeline-overview-memory {
+#timeline-overview-memory,
+#timeline-overview-power {
     position: absolute;
     left: 0;
     right: 0;
     bottom: 0;
     top: 20px;
     z-index: 160;
 }
 
-#timeline-overview-memory  {
+#timeline-overview-memory,
+#timeline-overview-power  {
     top: 25px;
 }
 
 #timeline-overview-pane {
     flex: 0 0 80px;
     position: relative;
     overflow: hidden;
 }
 
 #timeline-overview-container {
@@ skipping 179 matching lines @@
 }
 
 .timeline-overview-sidebar-frames .icon {
     -webkit-mask-position: -160px -48px;
 }
 
 .timeline-overview-sidebar-memory .icon {
     -webkit-mask-position: -224px -48px;
 }
 
+.timeline-overview-sidebar-power .icon {
+    -webkit-mask-position: -64px -120px;
+}
+
 .memory-graph-label {
     position: absolute;
     left: 5px;
     font-size: 9px;
     color: rgb(50%, 50%, 50%);
     white-space: nowrap;
 }
 
 .max.memory-graph-label {
     top: 5px;
@@ skipping 314 matching lines @@
     display: none;
 }
 
 .timeline-flamechart-view .flame-chart-main-pane .resources-divider-label {
     text-align: center;
 }
 
 .timeline-flamechart {
     overflow: hidden;
 }