Fix IWYU for BrowserThread::

Missing includes are blocking a bigger upcoming change that
removes browser_thread.h from other places which tend to have a far
reach.

This removal was done by a script which adds browser_thread.h if
the file has "BrowserThread::" on a line which isn't a comment.

If the file is a header it also substracts the include from matching .cc
file if any.

If the file is a .cc it omits the include if it's already in the
matching .h

Minor exceptions :
 * files that already included test_browser_thread.h (not doing so
   broke DEPS as some tests are explicitly allowed to include
   test_browser_thread.h but no content/public)
 * chrome/renderer/chrome_content_renderer_client_browsertest.cc
   (because it violates DEPS already by using BrowserThread:: from
    content/renderer but this CL doesn't aim to fix tricky use cases)

[email protected]

Bug: 815225, 821034
Change-Id: I5274433918c85f26caaa5b99adb990f07222fb99
Reviewed-on: https://chromium-review.googlesource.com/967186
Reviewed-by: Gabriel Charette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#543834}
diff --git a/content/browser/browser_main_loop_unittest.cc b/content/browser/browser_main_loop_unittest.cc
index 28451f3e..61ec07ae 100644
--- a/content/browser/browser_main_loop_unittest.cc
+++ b/content/browser/browser_main_loop_unittest.cc
@@ -9,6 +9,7 @@
 #include "base/sys_info.h"
 #include "base/task_scheduler/task_scheduler.h"
 #include "base/test/scoped_command_line.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "testing/gtest/include/gtest/gtest.h"