Update from https://crrev.com/305340

build/sanitizers/sanitizers.gyp

Index: build/sanitizers/sanitizers.gyp
diff --git a/build/sanitizers/sanitizers.gyp b/build/sanitizers/sanitizers.gyp
index d971d6d1c35b1e905b6f11f9fc23d57b755f26a9..64f7cdfc363d5223cdc6a345fc25c9f8fe681e20 100644
--- a/build/sanitizers/sanitizers.gyp
+++ b/build/sanitizers/sanitizers.gyp
@@ -56,6 +56,27 @@
         ],
       },
     },
+    {
+      # Copy llvm-symbolizer to the product dir so that LKGR bots can package it.
+      'target_name': 'llvm-symbolizer',
+      'type': 'none',
+      'variables': {
+
+       # Path is relative to this GYP file.
+       'llvm_symbolizer_path':
+           '../../third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer<(EXECUTABLE_SUFFIX)',
+      },
+      'conditions': [
+        ['clang==1', {
+          'copies': [{
+            'destination': '<(PRODUCT_DIR)',
+            'files': [
+              '<(llvm_symbolizer_path)',
+            ],
+          }],
+        }],
+      ],
+    },
   ],
 }