defeat cors attacks on audio/video tags

Neutralize error messages and fire no progress events
until media metadata has been loaded for media loaded
from cross-origin locations.

Bug: 828265, 826187
Change-Id: Iaf15ef38676403687d6a913cbdc84f2d70a6f5c6
Reviewed-on: https://chromium-review.googlesource.com/1015794
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Fredrik Hubinette <hubbe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557312}
void HTMLMediaElement::WaitForSourceChange() {
  BLINK_MEDIA_LOG << "waitForSourceChange(" << (void*)this << ")";

  StopPeriodicTimers();
  load_state_ = kWaitingForSource;

  SetNetworkState(kNetworkNoSource);

  SetShouldDelayLoadEvent(false);

  UpdateDisplayState();

  if (GetLayoutObject())
     GetLayoutObject()->UpdateFromElement();
 }

void HTMLMediaElement::WaitForSourceChange() {
  BLINK_MEDIA_LOG << "waitForSourceChange(" << (void*)this << ")";

  StopPeriodicTimers();
  load_state_ = kWaitingForSource;

  SetNetworkState(kNetworkNoSource);

  SetShouldDelayLoadEvent(false);

  UpdateDisplayState();

  if (GetLayoutObject())
     GetLayoutObject()->UpdateFromElement();
 }
