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 ce4a66351425101ca13707c357dbb10d858cd103..907c0007008efea3aa639de660a53080bd60b11c 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);