Merge pull request #8 from aroben/atom

InspectableWebContents should be able to accept existing WebContents.
Pull in latest libchromiumcontent to get gtest

* vendor/libchromiumcontent 0d607ee...4ae397b (1):
  > Build and distribute libgtest.a
Let embedders add their own protocol handlers
Fix DCHECK() assertion in BrowserClient
Update to latest libchromiumcontent

* vendor/libchromiumcontent 4ae397b...d5cef3b (1):
  > Add libtest_support_chromiumcontent.a
Allow embedders to provide their own ContentClient subclass
Allow embedders to specify extra .pak files
Turn off C++ exceptions

We weren't using them anyway, and don't intend to. This matches Chromium.
Fix crashes when dragging links

Turns out we needed to implement ContentClient::GetNativeImageNamed, which is
called to get the default drag image.
Temporarily use the libchromiumcontent contains my commit.