Merge to XFA: Add gmock to .gitignore

Original Review URL: https://codereview.chromium.org/985833002
TBR=halyavin@chromium.org

Review URL: https://codereview.chromium.org/985713004
diff --git a/.gitignore b/.gitignore
index 1269c12..623bf8d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 /build/Release
 /build/gyp
 /out
+/testing/gmock
 /testing/gtest
 /v8
 /xcodebuild