Don't leak TestPluginWebFrameClient in WebPluginContainerTests.

Don't leak TestPluginWebFrameClient in WebPluginContainerTests.

WebViewHelper::initializeAndLoad() doesn't take ownership of the optional
frame client parameter.  All other subclasses of TestWebFrameClient are
constructed on the stack too.

Fixes leaks like
Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0x5b2ea0 in operator new(unsigned long) /b/build/slave/ClangToTLinuxASan/build/src/third_party/llvm/compiler-rt/lib/asan/asan_new_delete.cc:62
    #    #1 0x1799216 in blink::WebPluginContainerTest_Copy_Test::TestBody() third_party/WebKit/Source/web/tests/WebPluginContainerTest.cpp:242:99
    #

BUG=523910, 245126, 494827
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201487

[Nico, 2015-08-29 21:28:27]

thakis@chromium.org changed reviewers:
+ creis@chromium.org

[Nico, 2015-08-29 21:28:28]

(I'd send this to nasko@ but he's OoO for a few more days.)

[Nico, 2015-08-29 21:38:36]

thakis@chromium.org changed reviewers:
+ chrishtr@chromium.org, pdr@chromium.org

[Nico, 2015-08-29 21:38:36]

+chrishtr, pdr who recently-ish added two such leaks in
https://codereview.chromium.org/1164683007

First to stamp wins!

[chrishtr, 2015-08-31 15:51:23]

The CQ bit was checked by chrishtr@chromium.org

[chrishtr, 2015-08-31 15:51:23]

lgtm

[commit-bot: I haz the power, 2015-08-31 15:51:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1308663004/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1308663004/40001

[commit-bot: I haz the power, 2015-08-31 17:59:22]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201487