[Telemetry] Expose v8's window.gc() method to the PerfTestRunner.

[Telemetry] Expose v8's window.gc() method to the PerfTestRunner.

Blink's PerfTestRunner has a gc method which tries to call
window.GCController.collect(), if it doesn't exist, it allocates a whole
bunch of memory to try to trigger a gc.

Since the blink_perf Measurement already passes --js-flags=--expose_gc,
we can call the window.gc() method instead of this hackery.

I'm hopeful that this will fix the Bindings/gc-tree.html crashes on
android.

BUG=252897
R=dtu@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=207975

[dtu, 2013-06-21 21:57:45]

Why all this when tab has a tab.CollectGarbage() method?

[tonyg, 2013-06-21 22:04:52]

On 2013/06/21 21:57:45, Dave Tu wrote:
> Why all this when tab has a tab.CollectGarbage() method?

The blink PerformanceTests access GC from JavaScript. There's not a good way to
call out to the python code from JS. For an example, see
third_party/WebKit/PerformanceTests/Bindings/gc-tree.html

[dtu, 2013-06-21 22:28:42]

lgtm

[commit-bot: I haz the power, 2013-06-21 22:38:29]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tonyg@chromium.org/17472007/1

[commit-bot: I haz the power, 2013-06-22 00:04:49]

Step "update" is always a major failure.
Look at the try server FAQ for more details.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_rel&...

[tonyg, 2013-06-22 00:36:51]

Committed patchset #1 manually as r207975 (presubmit successful).