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

Review URL: https://codereview.chromium.org/409723002

git-svn-id: svn://svn.chromium.org/blink/trunk@178601 bbb929c8-8fbe-4397-9dbb-9b2b20218538