Revert of cc: Adding BeginFrameTracker object and removing Now() from LTHI.

Revert of cc: Adding BeginFrameTracker object and removing Now() from LTHI. (patchset #17 id:320001 of https://codereview.chromium.org/787763006/)

Reason for revert:
May have caused Instrumentation test AndroidWebViewTest failures.
This is a speculative revert; I will re-land if nothing gets fixed.

http://build.chromium.org/p/chromium.linux/builders/Android%20Tests%20%28dbg%29/builds/27762/steps/Instrumentation%20test%20AndroidWebViewTest/logs/stdio

failures:
org.chromium.android_webview.test.AndroidScrollIntegrationTest#testFlingScrollOnPopup
org.chromium.android_webview.test.PopupWindowTest#testOnPageFinishedCalledOnDomModificationAfterNavigation
org.chromium.android_webview.test.PopupWindowTest#testPopupWindow
org.chromium.android_webview.test.PostMessageTest#testPostMessageToIframeInsidePopup

Original issue's description:
> cc: Adding BeginFrameTracker object and removing Now() from LTHI.
>
> **Sheriffs**: If this patch is making a test flaky / fail,
> then the test was already broken and this just makes the
> problem visible.
>
> This patch reduces the jitter in LTHI's animation time to
> be identical to the vsync jitter rather than being affected
> by the system load and OS scheduling delays.
>
> BeginFrameTracker uses DCHECKs and TRACE_EVENT to strictly
> track how the BeginFrameArgs are used throughout the LTHI.
> Using this information incorrect usage of Now() has been
> eliminated. Methods which violate correct usage of
> BeginFrameArgs are now clearly marked to prevent
> regressions.
>
> BUG=346230
>
> Committed: https://crrev.com/ce2671bf523d439ed7db7a606e871ca0416ef7a6
> Cr-Commit-Position: refs/heads/master@{#328911}

TBR=brianderson@chromium.org,skyostil@chromium.org,sunnyps@chromium.org,mithro@mithis.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=346230
Committed: https://crrev.com/f1a56b752fcac1a81dc86faff5840486be0cf709
Cr-Commit-Position: refs/heads/master@{#328937}

[Kunihiko Sakamoto, 2015-05-08 08:13:54]

Created Revert of cc: Adding BeginFrameTracker object and removing Now() from
LTHI.

[commit-bot: I haz the power, 2015-05-08 08:14:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1127313003/1

[commit-bot: I haz the power, 2015-05-08 08:15:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-08 08:16:07]

Patchset 1 (id:??) landed as
https://crrev.com/f1a56b752fcac1a81dc86faff5840486be0cf709
Cr-Commit-Position: refs/heads/master@{#328937}

[Kunihiko Sakamoto, 2015-05-08 09:49:33]

This revert appears to have fixed the test failures.