Listen for blur and focus events on window instead of canvas

Blur and focus events were not arriving for the canvas in
Firefox 35 and Chrome 40.

src/video/emscripten/SDL_emscriptenevents.c

@@ -586,8 +586,8 @@ Emscripten_RegisterEventHandlers(SDL_WindowData *data)
 
     emscripten_set_wheel_callback("#canvas", data, 0, Emscripten_HandleWheel);
 
-    emscripten_set_focus_callback("#canvas", data, 0, Emscripten_HandleFocus);
-    emscripten_set_blur_callback("#canvas", data, 0, Emscripten_HandleFocus);
+    emscripten_set_focus_callback("#window", data, 0, Emscripten_HandleFocus);
+    emscripten_set_blur_callback("#window", data, 0, Emscripten_HandleFocus);
 
     emscripten_set_touchstart_callback("#canvas", data, 0, Emscripten_HandleTouch);
     emscripten_set_touchend_callback("#canvas", data, 0, Emscripten_HandleTouch);
@@ -623,8 +623,8 @@ Emscripten_UnregisterEventHandlers(SDL_WindowData *data)
 
     emscripten_set_wheel_callback("#canvas", NULL, 0, NULL);
 
-    emscripten_set_focus_callback("#canvas", NULL, 0, NULL);
-    emscripten_set_blur_callback("#canvas", NULL, 0, NULL);
+    emscripten_set_focus_callback("#window", NULL, 0, NULL);
+    emscripten_set_blur_callback("#window", NULL, 0, NULL);
 
     emscripten_set_touchstart_callback("#canvas", NULL, 0, NULL);
     emscripten_set_touchend_callback("#canvas", NULL, 0, NULL);