Add builders for tracing event's structural arguments

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 c89da2f70d1460aba50c0a5629c19b7589aa4c5c..1dd9788f63982929824d355f516e4712f1f45c39 100644
--- a/cc/scheduler/scheduler_state_machine_unittest.cc
+++ b/cc/scheduler/scheduler_state_machine_unittest.cc
@@ -4,17 +4,18 @@
 
 #include "cc/scheduler/scheduler_state_machine.h"
 
+#include "base/debug/trace_event.h"
 #include "cc/scheduler/scheduler.h"
 #include "cc/test/begin_frame_args_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #define EXPECT_ACTION_UPDATE_STATE(action)                                   \
-  EXPECT_EQ(action, state.NextAction()) << *state.AsValue();                 \
+  EXPECT_EQ(action, state.NextAction()) << state.AsValue()->ToString();      \
   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();                                                 \
+        << state.AsValue()->ToString();                                      \
   }                                                                          \
   state.UpdateState(action);                                                 \
   if (action == SchedulerStateMachine::ACTION_NONE) {                        \
@@ -690,7 +691,7 @@ TEST(SchedulerStateMachineTest, TestNextActionDrawsOnBeginImplFrame) {
       state.SetNeedsCommit();
       EXPECT_NE(SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
                 state.NextAction())
-          << *state.AsValue();
+          << state.AsValue()->ToString();
     }
   }
 
@@ -716,16 +717,18 @@ TEST(SchedulerStateMachineTest, TestNextActionDrawsOnBeginImplFrame) {
     } else {
       expected_action = SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
       EXPECT_EQ(state.NextAction(), SchedulerStateMachine::ACTION_ANIMATE)
-          << *state.AsValue();
+          << state.AsValue()->ToString();
       state.UpdateState(state.NextAction());
     }
 
     // Case 1: needs_commit=false.
-    EXPECT_EQ(state.NextAction(), expected_action) << *state.AsValue();
+    EXPECT_EQ(state.NextAction(), expected_action)
+        << state.AsValue()->ToString();
 
     // Case 2: needs_commit=true.
     state.SetNeedsCommit();
-    EXPECT_EQ(state.NextAction(), expected_action) << *state.AsValue();
+    EXPECT_EQ(state.NextAction(), expected_action)
+        << state.AsValue()->ToString();
   }
 }
 
@@ -757,7 +760,7 @@ TEST(SchedulerStateMachineTest, TestNoCommitStatesRedrawWhenInvisible) {
       state.SetNeedsCommit();
       EXPECT_NE(SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
                 state.NextAction())
-          << *state.AsValue();
+          << state.AsValue()->ToString();
     }
   }
 }
@@ -1655,7 +1658,7 @@ TEST(SchedulerStateMachineTest, TestInitialActionsWhenContextLost) {
   // main thread will just abort anyway.
   state.SetVisible(false);
   EXPECT_EQ(SchedulerStateMachine::ACTION_NONE, state.NextAction())
-      << *state.AsValue();
+      << state.AsValue()->ToString();
 }
 
 TEST(SchedulerStateMachineTest, ReportIfNotDrawing) {