Revert "webrtc-internals: dont repaint invisible graphs"

This reverts commit e0de6d37.

Reason for revert: Speculatively reverting to try and fix compile error:

https://ci.chromium.org/buildbot/chromium.webkit/Android%20Builder/133884

https://logs.chromium.org/v/?s=chromium%2Fbb%2Fchromium.webkit%2FAndroid_Builder%2F133884%2F%2B%2Frecipes%2Fsteps%2Fcompile%2F0%2Fstdout


Original change's description:
> webrtc-internals: dont repaint invisible graphs
> 
> avoids repainting stats graphs that are not visible.
> Visibility is determined as described in
>   https://stackoverflow.com/a/21696585/4352772
> 
> BUG=678292
> 
> Change-Id: Ib7ac623f8d961359e4915b3f5580734fb1328bec
> Reviewed-on: https://chromium-review.googlesource.com/602270
> Reviewed-by: Tommi <tommi@chromium.org>
> Commit-Queue: Harald Alvestrand <hta@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#543372}

TBR=tommi@chromium.org,hta@chromium.org,philipp.hancke@googlemail.com

Change-Id: Id9328a3cc5275ae2143243055f575e142c88d943
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 678292
Reviewed-on: https://chromium-review.googlesource.com/963657Reviewed-by: Roger Tawa <rogerta@chromium.org>
Commit-Queue: Roger Tawa <rogerta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543377}

content/browser/resources/media/timeline_graph_view.js

@@ -149,13 +149,9 @@ var TimelineGraphView = (function() {
     },
 
     /**
-     * Draws the graph on |canvas_| when visible.
+     * Draws the graph on |canvas_|.
      */
     repaint: function() {
-      if (this.canvas_.offsetParent === null) {
-        return; // do not repaint graphs that are not visible.
-      }
-
       this.repaintTimerRunning_ = false;
 
       var width = this.canvas_.width;