Fix some missing const reference on function parameter.

This issue was found by a linter.

R=enne@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/23658023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221330 0039d316-1c4b-4281-b951-d872f2087c98

cc/resources/raster_worker_pool_perftest.cc

@@ -176,7 +176,7 @@ class RasterWorkerPoolPerfTest : public testing::Test {
     }
   }
 
-  void RunBuildTaskGraphTest(const std::string test_name,
+  void RunBuildTaskGraphTest(const std::string& test_name,
                              unsigned num_raster_tasks,
                              unsigned num_image_decode_tasks) {
     timer_.Reset();

cc/resources/tile_manager_perftest.cc

@@ -126,7 +126,7 @@ class TileManagerPerfTest : public testing::Test {
     CreateBinTiles(count - 3 * count_per_bin, NEVER_BIN, tiles);
   }
 
-  void RunManageTilesTest(const std::string test_name,
+  void RunManageTilesTest(const std::string& test_name,
                           unsigned tile_count,
                           unsigned priority_change_percent) {
     DCHECK_GE(tile_count, 100u);

cc/resources/worker_pool_perftest.cc

@@ -160,13 +160,13 @@ class WorkerPoolPerfTest : public testing::Test {
     worker_pool_->CheckForCompletedTasks();
   }
 
-  void AfterTest(const std::string test_name) {
+  void AfterTest(const std::string& test_name) {
     // Format matches chrome/test/perf/perf_test.h:PrintResult
     printf(
         "*RESULT %s: %.2f runs/s\n", test_name.c_str(), timer_.LapsPerSecond());
   }
 
-  void RunScheduleTasksTest(const std::string test_name,
+  void RunScheduleTasksTest(const std::string& test_name,
                             unsigned max_depth,
                             unsigned num_children_per_node) {
     timer_.Reset();
@@ -186,7 +186,7 @@ class WorkerPoolPerfTest : public testing::Test {
                            timer_.LapsPerSecond(), "runs/s", true);
   }
 
-  void RunExecuteTasksTest(const std::string test_name,
+  void RunExecuteTasksTest(const std::string& test_name,
                            unsigned max_depth,
                            unsigned num_children_per_node) {
     timer_.Reset();