Revert of Fix Performance::now() for browser navigations.

Revert of Fix Performance::now() for browser navigations. (https://codereview.chromium.org/379873002/)

Reason for revert:
Broke org.chromium.android_webview.test.AwContentsClientShouldOverrideUrlLoadingTest#testDoubleNavigateDoesNotSuppressInitialNavigate on the Android test bots.  See http://crbug.com/395817 .

Original issue's description:
> Fix Performance::now() for browser navigations.
> 
> Performance::now() is defined[1] as number of milliseconds since
> navigationStart. It works correctly for renderer-initiated navigations,
> but for browser-initiated ones we override the navigationStart with the
> recording taken on the browser side and this is not represented in
> Performace::now().
> 
> Among other reasons to be sad about this, this bug makes Chromium's
> pagecyclers not represent the renderer initialization times in their
> plt measurements.
> 
> This patch fixes this by adjusting the fields that are supposed to
> correspond to navigationStart when we change navigationStart from the
> embedder.
> 
> [1] http://www.w3.org/TR/hr-time/#dom-performance-now
> 
> BUG=376004
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178558

TBR=clamy@chromium.org,japhet@chromium.org,tonyg@chromium.org,ppi@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=376004
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178601

[Peter Kasting, 2014-07-21 23:22:48]

Created Revert of Fix Performance::now() for browser navigations.

[commit-bot: I haz the power, 2014-07-21 23:23:25]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/pkasting@chromium.org/409723002/1

[commit-bot: I haz the power, 2014-07-21 23:24:14]

Change committed as 178601