[Android WebView] Deflake new OnReceived*Error tests that simulate tap

[Android WebView] Deflake new OnReceived*Error tests that simulate tap

It seems that the first non-empty draw sometimes is missing the link that
the test is supposed to "tap". Waiting for the pixel colour to actually
change to the link colour stabilizes tests.

BUG=456782
Committed: https://crrev.com/029257f2c1b944b483eada3e5f05373b11175bfb
Cr-Commit-Position: refs/heads/master@{#321557}

[mnaganov (inactive), 2015-03-20 11:04:16]

mnaganov@chromium.org changed reviewers:
+ torne@chromium.org

[Torne, 2015-03-20 11:28:17]

lgtm

[mnaganov (inactive), 2015-03-20 11:29:00]

The CQ bit was checked by mnaganov@chromium.org

[commit-bot: I haz the power, 2015-03-20 11:29:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1026723002/1

[commit-bot: I haz the power, 2015-03-20 12:12:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-20 12:12:37]

Patchset 1 (id:??) landed as
https://crrev.com/029257f2c1b944b483eada3e5f05373b11175bfb
Cr-Commit-Position: refs/heads/master@{#321557}