[Mac] Move ScopedSendingEvent from content/common/mac to base/mac.

base/test/mock_chrome_application_mac.mm

Index: base/test/mock_chrome_application_mac.mm
diff --git a/base/test/mock_chrome_application_mac.mm b/base/test/mock_chrome_application_mac.mm
index 48db4195cab976a24270326892ee0970ecefa6ed..b0b86171d75481b1438fb5b184188699e2f6504b 100644
--- a/base/test/mock_chrome_application_mac.mm
+++ b/base/test/mock_chrome_application_mac.mm
@@ -4,22 +4,38 @@
 
 #include "base/test/mock_chrome_application_mac.h"
 
+#include "base/auto_reset.h"
 #include "base/logging.h"
 
 @implementation MockCrApp
+
++ (NSApplication*)sharedApplication {
+  NSApplication* app = [super sharedApplication];
+  DCHECK([app conformsToProtocol:@protocol(CrAppControlProtocol)])
+      << "Existing NSApp (class " << [[app className] UTF8String]
+      << ") does not conform to required protocol.";
+  return app;
+}
+
+- (void)sendEvent:(NSEvent*)event {
+  AutoReset<BOOL> scoper(&handlingSendEvent_, YES);
+  [super sendEvent:event];
+}
+
+- (void)setHandlingSendEvent:(BOOL)handlingSendEvent {
+  handlingSendEvent_ = handlingSendEvent;
+}
+
 - (BOOL)isHandlingSendEvent {
-  return NO;
+  return handlingSendEvent_;
 }
+
 @end
 
 namespace mock_cr_app {
 
 void RegisterMockCrApp() {
-  NSApplication* app = [MockCrApp sharedApplication];
-
-  // Would prefer ASSERT_TRUE() to provide better test failures, but
-  // this class is used by remoting/ for a non-test use.
-  DCHECK([app conformsToProtocol:@protocol(CrAppProtocol)]);
+  [MockCrApp sharedApplication];
 }
 
 }  // namespace mock_cr_app