Add start/stop listening Platform methods for Screen Orientation.

Source/modules/screen_orientation/ScreenOrientationController.cpp

Index: Source/modules/screen_orientation/ScreenOrientationController.cpp
diff --git a/Source/modules/screen_orientation/ScreenOrientationController.cpp b/Source/modules/screen_orientation/ScreenOrientationController.cpp
index 0e1520d5e3d921f0d0ff7dd9954f2811c033780a..ba39015a566a473c51787c7665b6e553dc66339d 100644
--- a/Source/modules/screen_orientation/ScreenOrientationController.cpp
+++ b/Source/modules/screen_orientation/ScreenOrientationController.cpp
@@ -12,6 +12,7 @@
 #include "modules/screen_orientation/ScreenOrientation.h"
 #include "platform/LayoutTestSupport.h"
 #include "platform/PlatformScreen.h"
+#include "public/platform/Platform.h"
 #include "public/platform/WebScreenOrientationClient.h"
 
 namespace WebCore {
@@ -43,6 +44,7 @@ ScreenOrientationController::ScreenOrientationController(LocalFrame& frame, blin
     : PageLifecycleObserver(frame.page())
     , m_client(client)
     , m_frame(frame)
+    , m_platformListening(false)
 {
 }
 
@@ -95,6 +97,8 @@ void ScreenOrientationController::updateOrientation()
 
 void ScreenOrientationController::pageVisibilityChanged()
 {
+    notifyPlatform();
+
     if (!m_orientation || !page() || page()->visibilityState() != PageVisibilityStateVisible)
         return;
 
@@ -145,6 +149,8 @@ void ScreenOrientationController::setOrientation(ScreenOrientation* orientation)
     m_orientation = orientation;
     if (m_orientation)
         updateOrientation();
+
+    notifyPlatform();
 }
 
 void ScreenOrientationController::lock(blink::WebScreenOrientationLockType orientation, blink::WebLockOrientationCallback* callback)
@@ -170,6 +176,18 @@ const LocalFrame& ScreenOrientationController::frame() const
     return m_frame;
 }
 
+void ScreenOrientationController::notifyPlatform()
+{
+    bool shouldListen = !!m_orientation && page() && page()->visibilityState() == PageVisibilityStateVisible;
+
+    if (m_platformListening == shouldListen)
+        return;
+
+    shouldListen ? blink::Platform::current()->startScreenOrientationListening()
+        : blink::Platform::current()->stopScreenOrientationListening();
+    m_platformListening = shouldListen;
+}
+
 void ScreenOrientationController::trace(Visitor* visitor)
 {
     visitor->trace(m_orientation);