Merge third_party/mesa/src from https://chromium.googlesource.com/chromium/deps/mesa.git at 9731cb962963bca8a05f3d0f6ea40c3a781f0537

This commit was generated by merge_from_chromium.py.

Change-Id: I8b774ee18c889edd120179ae169dfb6b59243c9e