browser_tests failing on chromium.memory/Linux ChromiumOS MSan Tests

Builders failed on: 
- Linux ChromiumOS MSan Tests: 
  https://build.chromium.org/p/chromium.memory/builders/Linux%20ChromiumOS%20MSan%20Tests

The cause of this failure appears to be a use-of-uninitialized-value warning from MSan being triggered on many tests. The likely culprit for this error is code added in https://chromium-review.googlesource.com/611324.