Battery Status API: add testing support for LayoutTests.

content/public/test/layouttest_support.h

Index: content/public/test/layouttest_support.h
diff --git a/content/public/test/layouttest_support.h b/content/public/test/layouttest_support.h
index cf4e695cb1cae695516071ef4c3ce6c5cf153aa5..76a4deec13747a4d7e2f26d475da8b10b4bfc146 100644
--- a/content/public/test/layouttest_support.h
+++ b/content/public/test/layouttest_support.h
@@ -12,6 +12,7 @@
 #include "third_party/WebKit/public/platform/WebScreenOrientationType.h"
 
 namespace blink {
+class WebBatteryStatus;
 class WebDeviceMotionData;
 class WebDeviceOrientationData;
 class WebGamepad;
@@ -67,6 +68,9 @@ void SetMockScreenOrientation(
 // Resets the mock screen orientation data.
 void ResetMockScreenOrientation();
 
+// Notifies blink that battery status has changed.
+void MockBatteryStatusChanged(const blink::WebBatteryStatus& status);
+
 // Returns the length of the local session history of a render view.
 int GetLocalSessionHistoryLength(RenderView* render_view);