Adding a ToPrettyString method to ConvertableToTracedValue.

cc/scheduler/scheduler_state_machine_unittest.cc

Index: cc/scheduler/scheduler_state_machine_unittest.cc
diff --git a/cc/scheduler/scheduler_state_machine_unittest.cc b/cc/scheduler/scheduler_state_machine_unittest.cc
index 0f66a7374acf50e2cc3550274e37b97b526a3824..0d59f9212293a1371d443f791d38e496fea0ce11 100644
--- a/cc/scheduler/scheduler_state_machine_unittest.cc
+++ b/cc/scheduler/scheduler_state_machine_unittest.cc
@@ -10,12 +10,14 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 #define EXPECT_ACTION_UPDATE_STATE(action)                                   \
-  EXPECT_EQ(action, state.NextAction()) << state.AsValue()->ToString();      \
+  EXPECT_STREQ(SchedulerStateMachine::ActionToString(action),                \
+               SchedulerStateMachine::ActionToString(state.NextAction()))    \
+      << state.AsValue()->ToPrettyString();                                  \
   if (action == SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE ||   \
       action == SchedulerStateMachine::ACTION_DRAW_AND_SWAP_FORCED) {        \
     EXPECT_EQ(SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE, \
               state.begin_impl_frame_state())                                \
-        << state.AsValue()->ToString();                                      \
+        << state.AsValue()->ToPrettyString();                                \
   }                                                                          \
   state.UpdateState(action);                                                 \
   if (action == SchedulerStateMachine::ACTION_NONE) {                        \