Too large plugins are crashing.
https://bugs.webkit.org/show_bug.cgi?id=139856

Reviewed by Darin Adler.

Source/WebKit2:

* WebProcess/Plugins/PluginProxy.cpp:
(WebKit::PluginProxy::updateBackingStore): Return false if backingStore cannot be allocated.

LayoutTests:

Add layout test to cover this crash.

* plugins/large-plugin-crash-expected.txt: Added.
* plugins/large-plugin-crash.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@177824 268f45cc-cd09-0410-ab3c-d52691b4dbfc