Roll chromium_revision b2c6a86..e937e5f (332773:333350)

Add symlink to third_party/android_platform to handle changes in
https://codereview.chromium.org/1072533002

Relevant changes:
* src/third_party/boringssl/src: 8a228f5..af0e32c
* src/third_party/icu: f1ad7f9..9939a5d
* src/third_party/libvpx: 654e661..a436311
* src/third_party/libyuv: 35aa92a..632c50f
* src/tools/gyp: 29e94a3..fdc7b81
Details: https://chromium.googlesource.com/chromium/src/+/b2c6a86..e937e5f/DEPS

Clang version was not updated in this roll.

BUG=
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1169083002.

Cr-Commit-Position: refs/heads/master@{#9400}