Add allocator.gyp target to gpu_unittests to fix heapcheck build

gpu/gpu.gyp

Index: gpu/gpu.gyp
diff --git a/gpu/gpu.gyp b/gpu/gpu.gyp
index 9c72995eb40ec2163ea093bb30f9ebb62e201cbb..026aad5f10eec50a5857eb8073525bc47365712b 100644
--- a/gpu/gpu.gyp
+++ b/gpu/gpu.gyp
@@ -228,6 +228,12 @@
             '../testing/android/native_test.gyp:native_test_native_code',
           ],
         }],
+        # See http://crbug.com/162998#c4 for why this is needed.
+        ['OS=="linux" and linux_use_tcmalloc==1', {
+          'dependencies': [
+            '../base/allocator/allocator.gyp:allocator',
+          ],
+        }],
       ],
       # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],