Fix debug assertion about performing IO on the UI thread

We were querying the application's FILEVERSIONINFO every time we needed to
figure out the path for storing BrowserContext data. Now we cache the path the
first time we need it, which is during application initialization and before IO
prohibitions begin.
Implement undocked dev tools on Windows

DevToolsWindow represents a vanilla top-level window that shows the dev tools.
It uses ui::WindowImpl to implement window functionality, which requires a
newer libchromiumcontent which contains the necessary headers for using that
class, and requires some modifications to brightray.gypi to make WTL's  headers
available.

* vendor/libchromiumcontent 2f53a96...fc02d93 (4):
  > Export third_party/wtl/include headers
  > Export test_support_base.pdb and test_support_content.pdb
  > Fix linker errors with test_support_base on Windows
  > Fix linker errors with base_prefs_test_support on Windows