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- Correct the URL of the public Google ObjC style guide.
- Correct the guide to no longer assert that Google ObjC style "inherits"
  from C++ style.

TBR: eugenebut@chromium.org
Bug: 
Change-Id: I67c42c648536d8c0d1fbcd3cfef98424c811bdb1
Reviewed-on: https://chromium-review.googlesource.com/725327Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509738}