Add an optimize_for_fuzzing GN flag to build with -O1

build/config/compiler/compiler.gni

Index: build/config/compiler/compiler.gni
diff --git a/build/config/compiler/compiler.gni b/build/config/compiler/compiler.gni
index cc8f5a1472e7cfd2975790cb2de164cd51810b3d..e473d4cca32a2f8dbfd58b34e8033a2c0804b02b 100644
--- a/build/config/compiler/compiler.gni
+++ b/build/config/compiler/compiler.gni
@@ -47,6 +47,10 @@ declare_args() {
   #
   # TODO(sebmarchand): Add support for the PGU (update) phase.
   chrome_pgo_phase = 0
+
+  # Optimize for coverage guided fuzzing (balance between speed and number of
+  # branches)
+  optimize_for_fuzzing = false

[Dirk Pranke, 2016/10/03 20:37:13]

If this doesn't need to be referenced outside of
//build/config/compiler/BUILD.gn, you should put this in the declare_args()
block in that file.

[Oliver Chang, 2016/10/03 20:54:25]

Done.

 }
 
 declare_args() {