Blink revision fix
Blink revision fix

The previous code wasn't accounting for triggered builds correctly (triggered
builds should always be using parent_got_revisions).

This makes it so that revision resolution is always done in 3 phases
1. Get src/webkit revision from parent properties
2. If step 1 didn't resolve it, then get it from the source stamp
3. If step 1/2 didn't resovle it, set it to HEAD

Also fixed blink_config, this should only activate when its set to 'blink', because otherwise its set to 'chromium' and this always activates.

BUG=373456

Review URL: https://codereview.chromium.org/401703002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@283920 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build