Implemented ForceMaximizeBrowserWindowOnFirstRun policy, added unit test and browser test.

ash/shell_delegate.h

Index: ash/shell_delegate.h
diff --git a/ash/shell_delegate.h b/ash/shell_delegate.h
index 148f6867ca331a981be886ccc024a4bbb85e5ff4..db51d028f0947ea4272040fc06c7aa17d54b7d06 100644
--- a/ash/shell_delegate.h
+++ b/ash/shell_delegate.h
@@ -83,6 +83,11 @@ class ASH_EXPORT ShellDelegate {
   // Returns true if multi account is enabled.
   virtual bool IsMultiAccountEnabled() const = 0;
 
+  // Returns true if the first window shown on first run should be
+  // unconditionally maximized, overriding the heuristic that normally chooses
+  // the window size.
+  virtual bool ForceMaximizeOnFirstRun() const = 0;
+
   // Called before processing |Shell::Init()| so that the delegate
   // can perform tasks necessary before the shell is initialized.
   virtual void PreInit() = 0;