Oilpan: improve resource-tree-mimetype.html stability.

Oilpan: improve resource-tree-mimetype.html stability.

The http/tests/inspector-enabled/resource-tree/resource-tree-mimetype.html
test enumerates the current set of registered resources, showing their
properties.

With Oilpan enabled, the registered resources might include ones which are
no longer alive, but not yet finalized. So as to ensure a consistent
resource baseline for the test, force a GC before initiating the test.

R=haraken
BUG=462935
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191061

[sof, 2015-03-01 16:13:11]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2015-03-01 16:13:12]

Please take a look.

To get stable output from this test when not running in a pristine renderer
process, an explicit gc() seems unavoidable with Resource objects being on the
heap.

[haraken, 2015-03-01 16:31:09]

LGTM

[sof, 2015-03-01 17:22:16]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2015-03-01 17:28:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/964173002/1

[commit-bot: I haz the power, 2015-03-01 17:31:22]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191061