Rename RenderProcessHost::IsGuest to RenderProcessHost::IsIsolatedGuest

Not all guests are created equal. <webview> guests are isolated from other processes.
In other words, the content of a <webview> cannot live in the same process as any other
non-<webview> content.

This is not true for <appview>. <appview> guests are NOT isolated. In the future,
BrowserPluginGuest::IsGuest and GuestViewBase::IsGuest may return true even if
RenderProcessHost::IsIsolatedGuest returns false.

BUG=364141, 330264

Review URL: https://codereview.chromium.org/293093010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@273733 0039d316-1c4b-4281-b951-d872f2087c98
20 files changed