cc: Fix tile manager raster tile iterator perftest.

This test is currently broken, as it doesn't really reset the initial
conditions each run.

NOTE TO PERF SHERIFFS
---------------------

This is very likely to regress all of the
tile_manager_raster_tile_iterator tests. This is expected, as the test
currently doesn't do anything useful. This is a correctness fix for
that test.

R=reveman, enne

Review URL: https://codereview.chromium.org/283463003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269885 0039d316-1c4b-4281-b951-d872f2087c98

cc/resources/tile_manager_perftest.cc

@@ -299,16 +299,17 @@ class TileManagerTileIteratorPerfTest : public testing::Test,
     pending_layer_->SetAllTilesVisible();
   }
 
-  void RunTest(const std::string& test_name, unsigned tile_count) {
+  void RunTest(const std::string& test_name, int tile_count) {
     timer_.Reset();
     do {
+      int count = tile_count;
       for (TileManager::RasterTileIterator it(tile_manager(),
                                               SAME_PRIORITY_FOR_BOTH_TREES);
-           it && tile_count;
+           it && count;
            ++it) {
-        --tile_count;
+        --count;
       }
-      ASSERT_EQ(0u, tile_count);
+      ASSERT_EQ(0, count);
       timer_.NextLap();
     } while (!timer_.HasTimeLimitExpired());