Simplify "WouldTaintOrigin" concept in media/blink

Currently WebMediaPlayer has three predicates:
 - DidGetOpaqueResponseFromServiceWorker
 - HasSingleSecurityOrigin
 - DidPassCORSAccessCheck
. These are used to determine whether the response body is available
for scripts. They are known to be confusing, and actually
MediaElementAudioSourceHandler::WouldTaintOrigin misuses them.

This CL merges the three predicates to one, WouldTaintOrigin, to remove
the confusion. Now the "response type" concept is available and we
don't need a custom CORS check, so this CL removes
BaseAudioContext::WouldTaintOrigin. This CL also renames
URLData::has_opaque_data_ and its (direct and indirect) data accessors
to match the spec.

Bug: 849942, 875153
Change-Id: I6acf50169d7445c4ff614e80ac606f79ee577d2a
Reviewed-on: https://chromium-review.googlesource.com/c/1238098
Reviewed-by: Fredrik Hubinette <hubbe@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598258}
void UrlData::MergeFrom(const scoped_refptr<UrlData>& other) {
  if (ValidateDataOrigin(other->data_origin_)) {
    DCHECK(thread_checker_.CalledOnValidThread());
    valid_until_ = std::max(valid_until_, other->valid_until_);
    set_length(other->length_);
    cacheable_ |= other->cacheable_;
    range_supported_ |= other->range_supported_;
    if (last_modified_.is_null()) {
       last_modified_ = other->last_modified_;
     }
     bytes_read_from_cache_ += other->bytes_read_from_cache_;
    // is_cors_corss_origin_ will not relax from true to false.
    set_is_cors_cross_origin(other->is_cors_cross_origin_);
     multibuffer()->MergeFrom(other->multibuffer());
   }
 }

void UrlData::MergeFrom(const scoped_refptr<UrlData>& other) {
  if (ValidateDataOrigin(other->data_origin_)) {
    DCHECK(thread_checker_.CalledOnValidThread());
    valid_until_ = std::max(valid_until_, other->valid_until_);
    set_length(other->length_);
    cacheable_ |= other->cacheable_;
    range_supported_ |= other->range_supported_;
    if (last_modified_.is_null()) {
       last_modified_ = other->last_modified_;
     }
     bytes_read_from_cache_ += other->bytes_read_from_cache_;
    set_has_opaque_data(other->has_opaque_data_);
     multibuffer()->MergeFrom(other->multibuffer());
   }
 }
