Split application_test_main.cc out of *_base.cc.

mojo/public/cpp/application/application_test_base.h

Index: mojo/public/cpp/application/application_test_base.h
diff --git a/mojo/public/cpp/application/application_test_base.h b/mojo/public/cpp/application/application_test_base.h
index 7fe38d28f66872fdef00d46b4e18a12339f7f2b6..2f400a414ba27a128e69334182bb46d73198bc71 100644
--- a/mojo/public/cpp/application/application_test_base.h
+++ b/mojo/public/cpp/application/application_test_base.h
@@ -17,6 +17,10 @@ class ApplicationImpl;
 
 namespace test {
 
+// Access the shell handle shared by multiple test application instances.
+ScopedMessagePipeHandle PassShellHandle();
+void SetShellHandle(ScopedMessagePipeHandle handle);
+
 // A GTEST base class for application testing executed in mojo_shell.
 class ApplicationTestBase : public testing::Test {
  public: