Make snapshot_unittests depend on allocator.gyp:allocator when necessary

This fixes the heapchecker+components release build.

BUG=241938

Review URL: https://chromiumcodereview.appspot.com/15797009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203046 0039d316-1c4b-4281-b951-d872f2087c98

ui/snapshot/snapshot.gyp

@@ -66,6 +66,12 @@
             '../compositor/compositor.gyp:compositor_test_support',
           ],
         }],
+        # See http://crbug.com/162998#c4 for why this is needed.
+        ['OS=="linux" and linux_use_tcmalloc==1', {
+          'dependencies': [
+            '../../base/allocator/allocator.gyp:allocator',
+          ],
+        }],
       ],
     },
   ],