Roll chromium_revision a28d8d5..5482f56 (346100:347609)

Recent changes (https://codereview.chromium.org/1311013010) introduces a
dependency on WebKit (Blink) in Chromium, which forces us to start pulling
down that as well (+6GB). However Blink is about to be merged into the
Chromium repo soon anyway, so the size increase is inevitable.
Luckily, this can be removed in the next roll, if we roll past
http://crrev.com/348812

The ijar dependency was introduced in https://codereview.chromium.org/1323053003 (#347208)

Relevant changes:
* src/third_party/boringssl/src: 12fe1b2..ac8302a
* src/third_party/libvpx: a208eca..0304cef
* src/third_party/libyuv: 3c4f573..0bc626a
* src/tools/gyp: 6ee91ad..5d01a8c
Details: a28d8d5..5482f56/DEPS

Clang version was not updated in this roll.

R=torbjorng@webrtc.org
TBR=marpan@webrtc.org
BUG=webrtc:5005, chromium:530112

Review URL: https://codereview.webrtc.org/1305043008 .

Cr-Commit-Position: refs/heads/master@{#9956}

.gn

@@ -42,5 +42,6 @@ exec_script_whitelist = [
   "//build/toolchain/win/BUILD.gn",
   "//third_party/boringssl/BUILD.gn",
   "//third_party/opus/BUILD.gn",
+  "//third_party/WebKit/Source/config.gni",
   "//webrtc/modules/video_render/BUILD.gn",
 ]