Update Gamepad API to match the latest specification

ppapi/shared_impl/ppb_gamepad_shared.h

Index: ppapi/shared_impl/ppb_gamepad_shared.h
diff --git a/ppapi/shared_impl/ppb_gamepad_shared.h b/ppapi/shared_impl/ppb_gamepad_shared.h
index c6f535d3d14ecb97f9455624f3a468afc66104f2..22b4df7a7be1477f698feb0f6c826904c4c571ef 100644
--- a/ppapi/shared_impl/ppb_gamepad_shared.h
+++ b/ppapi/shared_impl/ppb_gamepad_shared.h
@@ -19,7 +19,7 @@ namespace ppapi {
 
 struct WebKitGamepadButton {
   bool pressed;
-  float value;
+  double value;
 };
 
 // This must match the definition of blink::Gamepad. The GamepadHost unit test
@@ -44,7 +44,7 @@ struct WebKitGamepad {
   unsigned axes_length;
 
   // Normalized values representing axes, in the range [-1..1].
-  float axes[kAxesLengthCap];
+  double axes[kAxesLengthCap];
 
   // Number of valid entries in the buttons array.
   unsigned buttons_length;