Introduce CancelUponDeferral() to buffered media loaders.

Fixes hitting the maximum connection limit of 6 per domain when a
media tag is used with preload=metadata.

Deferred network connections will be cancelled once reaching the
HAVE_ENOUGH_DATA state for preload=metadata, non-streaming
resources that have not started playback.

A soft cancel is introduced which allows us to preserve the data
cached thus far in the BufferedResourceLoader. Once this cache is
exhausted the loader will fulfill subsequent reads with a cache
miss and continue on as normal.

preload=metadata intentionally does not cache enough data for a
smooth playback experience on slow connections, so the cache miss
here does not increase jank relative to the current status quo.

For similar reasons, since preload=auto does load enough data for
an uninterrupted playback, we can't use this method there or we'll
introduce jank during the cache miss and subsequent catch up.

Note: This does not resolve hung connections if multiple media
elements are actually playing back or if they are served from
a server without range requests.

Note 2: This also fixes a broken media_blink_unittests, which was
missing some Gin dependency.

BUG=162627
TEST=new unittest, passes layout tests.

Review URL: https://codereview.chromium.org/1029763002

Cr-Commit-Position: refs/heads/master@{#322610}

1 files changed, 1 insertions, 0 deletions

diff --git a/media/blink/media_blink.gyp b/media/blink/media_blink.gyp
index fa6042f..9a697e6 100644
--- a/media/blink/media_blink.gyp
+++ b/media/blink/media_blink.gyp
@@ -95,6 +95,7 @@
         '../../base/base.gyp:test_support_base',
         '../../cc/cc.gyp:cc',
         '../../cc/blink/cc_blink.gyp:cc_blink',
+        '../../gin/gin.gyp:gin',
         '../../net/net.gyp:net',
         '../../testing/gmock.gyp:gmock',
         '../../testing/gtest.gyp:gtest',