PlzNavigate: use the right helper functions in OverscrollNavigationOverlayTests

PlzNavigate: use the right helper functions in OverscrollNavigationOverlayTests

This CL modifies OverscrollNavigationOverlayTests so that they use
TestRenderFrameHost::PrepareForCommit and TestRenderFrameHost::SendNavigate
instead of TestWebContents::CommitPendingNavigation. This allows values for
CrossNavigationPending to be properly set with browser-side navigation.

BUG=439423
Committed: https://crrev.com/73d097cbe1db3f780eb30d5fb88713066d2560f7
Cr-Commit-Position: refs/heads/master@{#325427}

[clamy, 2015-04-14 15:10:19]

clamy@chromium.org changed reviewers:
+ carlosk@chromium.org, fdegans@chromium.org, nasko@chromium.org,
sadrul@chromium.org

[clamy, 2015-04-14 15:11:19]

@nasko, sadrul: PTAL
@carlosk, fdegans: FYI
This fixes the test failures on the browser-side-navigation bot caused by the
introduction of new tests in https://codereview.chromium.org/1072123002.

[nasko, 2015-04-14 16:13:35]

LGTM

https://codereview.chromium.org/1088933003/diff/1/content/browser/web_content...
File content/browser/web_contents/aura/overscroll_navigation_overlay_unittest.cc
(right):

https://codereview.chromium.org/1088933003/diff/1/content/browser/web_content...
content/browser/web_contents/aura/overscroll_navigation_overlay_unittest.cc:256:
main_test_rfh()->SendNavigate(
nit: I kinda like the CommitPendingNavigation paradigm, as this test doesn't
really care about how navigation is done, but this CL is likely not the place to
figure out how to make this better.

[clamy, 2015-04-16 12:18:45]

The CQ bit was checked by clamy@chromium.org

[commit-bot: I haz the power, 2015-04-16 12:18:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1088933003/1

[commit-bot: I haz the power, 2015-04-16 12:56:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-16 12:57:11]

Patchset 1 (id:??) landed as
https://crrev.com/73d097cbe1db3f780eb30d5fb88713066d2560f7
Cr-Commit-Position: refs/heads/master@{#325427}