signin: force web signin flow initiated visits to accounts.google.com to their own process.

chrome/browser/signin/signin_manager.h

Index: chrome/browser/signin/signin_manager.h
diff --git a/chrome/browser/signin/signin_manager.h b/chrome/browser/signin/signin_manager.h
index 2272c7acc0d17dc479fdf403ea2052941bd8b484..f5388e3af714c64f2fc28d56b406acf975ce7812 100644
--- a/chrome/browser/signin/signin_manager.h
+++ b/chrome/browser/signin/signin_manager.h
@@ -195,6 +195,9 @@ class SigninManager : public GaiaAuthConsumer,
   // ignored).
   bool IsSignoutProhibited() const;
 
+  void SetSigninProcess(int process_id);
+  bool IsSigninProcess(int process_id) const;
+
  protected:
   // Weak pointer to parent profile (protected so FakeSigninManager can access
   // it).
@@ -331,6 +334,7 @@ class SigninManager : public GaiaAuthConsumer,
 
   base::WeakPtrFactory<SigninManager> weak_pointer_factory_;
 
+  int signin_process_id_;
 
 #if defined(ENABLE_CONFIGURATION_POLICY) && !defined(OS_CHROMEOS)
   // CloudPolicyClient reference we keep while determining whether to create