Introduce background.scripts feature for extension manifests.

This optimizes for the common use case where background pages
just include a reference to one or more script files and no
additional HTML.

BUG=107791


Review URL: http://codereview.chromium.org/9150008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@117110 0039d316-1c4b-4281-b951-d872f2087c98
void TestingAutomationProvider::GetShelfVisibility(int handle, bool* visible) {
  *visible = false;

  if (browser_tracker_->ContainsHandle(handle)) {
    Browser* browser = browser_tracker_->GetResource(handle);
    if (browser) {
#if defined(OS_CHROMEOS)
      *visible = ActiveDownloadsUI::GetPopup();
#else
      *visible = browser->window()->IsDownloadShelfVisible();
#endif
    }
  }
}

void TestingAutomationProvider::GetShelfVisibility(int handle, bool* visible) {
  *visible = false;

  if (browser_tracker_->ContainsHandle(handle)) {
    Browser* browser = browser_tracker_->GetResource(handle);
    if (browser) {
#if defined(OS_CHROMEOS)
      *visible = ActiveDownloadsUI::GetPopup();
#else
      *visible = browser->window()->IsDownloadShelfVisible();
#endif
    }
  }
}
