cc: Adding creation location to debug BeginFrameArgs objects.

This allows easy tracing of a BeginFrameArgs object back to the
BeginFrameSource that created it. This is very useful as we have multiple
BeginFrameSources in the system now. The Primary / Background sources being a
perfect example.

While location tracking is highly optimised (as it is used in every base::Bind
calls) it doubles the size of BeginFrameArgs objects. Hence we only enable
location tracking in debug builds. In release builds we make sure to never
create the Location objects in the first place, so no extra strings are found
in the binary. This can be checked with the strings tool.

BUG=346230
DEPS=742683002

Review URL: https://codereview.chromium.org/735723005

Cr-Commit-Position: refs/heads/master@{#306326}

3 files changed, 67 insertions, 16 deletions

diff --git a/cc/output/begin_frame_args.cc b/cc/output/begin_frame_args.cc
index 0be9318..5744d9d 100644
--- a/cc/output/begin_frame_args.cc
+++ b/cc/output/begin_frame_args.cc
@@ -41,12 +41,19 @@ BeginFrameArgs::BeginFrameArgs(base::TimeTicks frame_time,
       type(type) {
 }
 
-BeginFrameArgs BeginFrameArgs::Create(base::TimeTicks frame_time,
+BeginFrameArgs BeginFrameArgs::Create(BeginFrameArgs::CreationLocation location,
+                                      base::TimeTicks frame_time,
                                       base::TimeTicks deadline,
                                       base::TimeDelta interval,
                                       BeginFrameArgs::BeginFrameArgsType type) {
   DCHECK_NE(type, BeginFrameArgs::INVALID);
+#ifdef NDEBUG
   return BeginFrameArgs(frame_time, deadline, interval, type);
+#else
+  BeginFrameArgs args = BeginFrameArgs(frame_time, deadline, interval, type);
+  args.created_from = location;
+  return args;
+#endif
 }
 
 scoped_refptr<base::debug::ConvertableToTraceFormat> BeginFrameArgs::AsValue()
@@ -63,6 +70,9 @@ void BeginFrameArgs::AsValueInto(base::debug::TracedValue* state) const {
   state->SetDouble("frame_time_us", frame_time.ToInternalValue());
   state->SetDouble("deadline_us", deadline.ToInternalValue());
   state->SetDouble("interval_us", interval.InMicroseconds());
+#ifndef NDEBUG
+  state->SetString("created_from", created_from.ToString());
+#endif
 }
 
 // This is a hard-coded deadline adjustment that assumes 60Hz, to be used in
diff --git a/cc/output/begin_frame_args.h b/cc/output/begin_frame_args.h
index 0be5241..ba29523 100644
--- a/cc/output/begin_frame_args.h
+++ b/cc/output/begin_frame_args.h
@@ -5,6 +5,7 @@
 #ifndef CC_OUTPUT_BEGIN_FRAME_ARGS_H_
 #define CC_OUTPUT_BEGIN_FRAME_ARGS_H_
 
+#include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "base/values.h"
@@ -17,6 +18,22 @@ class TracedValue;
 }
 }
 
+/**
+ * In debug builds we trace the creation origin of BeginFrameArgs objects. We
+ * reuse the tracked_objects::Location system to do that.
+ *
+ * However, in release builds we don't want this as it doubles the size of the
+ * BeginFrameArgs object. As well it adds a number of largish strings to the
+ * binary. Despite the argument being unused, most compilers are unable to
+ * optimise it away even when unused. Instead we use the BEGINFRAME_FROM_HERE
+ * macro to prevent the data even getting referenced.
+ */
+#ifdef NDEBUG
+#define BEGINFRAME_FROM_HERE nullptr
+#else
+#define BEGINFRAME_FROM_HERE FROM_HERE
+#endif
+
 namespace cc {
 
 struct CC_EXPORT BeginFrameArgs {
@@ -31,9 +48,18 @@ struct CC_EXPORT BeginFrameArgs {
   // Creates an invalid set of values.
   BeginFrameArgs();
 
+#ifdef NDEBUG
+  typedef const void* CreationLocation;
+#else
+  typedef const tracked_objects::Location& CreationLocation;
+  tracked_objects::Location created_from;
+#endif
+
   // You should be able to find all instances where a BeginFrame has been
   // created by searching for "BeginFrameArgs::Create".
-  static BeginFrameArgs Create(base::TimeTicks frame_time,
+  // The location argument should **always** be BEGINFRAME_FROM_HERE macro.
+  static BeginFrameArgs Create(CreationLocation location,
+                               base::TimeTicks frame_time,
                                base::TimeTicks deadline,
                                base::TimeDelta interval,
                                BeginFrameArgsType type);
diff --git a/cc/output/begin_frame_args_unittest.cc b/cc/output/begin_frame_args_unittest.cc
index 9d77a45d..877a857 100644
--- a/cc/output/begin_frame_args_unittest.cc
+++ b/cc/output/begin_frame_args_unittest.cc
@@ -15,26 +15,29 @@ namespace {
 
 TEST(BeginFrameArgsTest, Helpers) {
   // Quick create methods work
-  BeginFrameArgs args0 = CreateBeginFrameArgsForTesting();
+  BeginFrameArgs args0 = CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE);
   EXPECT_TRUE(args0.IsValid()) << args0;
 
-  BeginFrameArgs args1 = CreateBeginFrameArgsForTesting(0, 0, -1);
+  BeginFrameArgs args1 =
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 0, 0, -1);
   EXPECT_FALSE(args1.IsValid()) << args1;
 
-  BeginFrameArgs args2 = CreateBeginFrameArgsForTesting(1, 2, 3);
+  BeginFrameArgs args2 =
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 1, 2, 3);
   EXPECT_TRUE(args2.IsValid()) << args2;
   EXPECT_EQ(1, args2.frame_time.ToInternalValue());
   EXPECT_EQ(2, args2.deadline.ToInternalValue());
   EXPECT_EQ(3, args2.interval.ToInternalValue());
   EXPECT_EQ(BeginFrameArgs::NORMAL, args2.type);
 
-  BeginFrameArgs args3 = CreateExpiredBeginFrameArgsForTesting();
+  BeginFrameArgs args3 =
+      CreateExpiredBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE);
   EXPECT_TRUE(args3.IsValid()) << args3;
   EXPECT_GT(gfx::FrameTime::Now(), args3.deadline);
   EXPECT_EQ(BeginFrameArgs::NORMAL, args3.type);
 
-  BeginFrameArgs args4 =
-      CreateBeginFrameArgsForTesting(1, 2, 3, BeginFrameArgs::MISSED);
+  BeginFrameArgs args4 = CreateBeginFrameArgsForTesting(
+      BEGINFRAME_FROM_HERE, 1, 2, 3, BeginFrameArgs::MISSED);
   EXPECT_TRUE(args4.IsValid()) << args4;
   EXPECT_EQ(1, args4.frame_time.ToInternalValue());
   EXPECT_EQ(2, args4.deadline.ToInternalValue());
@@ -42,16 +45,19 @@ TEST(BeginFrameArgsTest, Helpers) {
   EXPECT_EQ(BeginFrameArgs::MISSED, args4.type);
 
   // operator==
-  EXPECT_EQ(CreateBeginFrameArgsForTesting(4, 5, 6),
-            CreateBeginFrameArgsForTesting(4, 5, 6));
+  EXPECT_EQ(CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 4, 5, 6),
+            CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 4, 5, 6));
 
   EXPECT_NONFATAL_FAILURE(
-      EXPECT_EQ(CreateBeginFrameArgsForTesting(7, 8, 9, BeginFrameArgs::MISSED),
-                CreateBeginFrameArgsForTesting(7, 8, 9)),
+      EXPECT_EQ(CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 7, 8, 9,
+                                               BeginFrameArgs::MISSED),
+                CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 7, 8, 9)),
+      "");
+
+  EXPECT_NONFATAL_FAILURE(
+      EXPECT_EQ(CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 4, 5, 6),
+                CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, 7, 8, 9)),
       "");
-  EXPECT_NONFATAL_FAILURE(EXPECT_EQ(CreateBeginFrameArgsForTesting(4, 5, 6),
-                                    CreateBeginFrameArgsForTesting(7, 8, 9)),
-                          "");
 
   // operator<<
   std::stringstream out1;
@@ -74,7 +80,7 @@ TEST(BeginFrameArgsTest, Create) {
   EXPECT_FALSE(args1.IsValid()) << args1;
 
   BeginFrameArgs args2 = BeginFrameArgs::Create(
-      base::TimeTicks::FromInternalValue(1),
+      BEGINFRAME_FROM_HERE, base::TimeTicks::FromInternalValue(1),
       base::TimeTicks::FromInternalValue(2),
       base::TimeDelta::FromInternalValue(3), BeginFrameArgs::NORMAL);
   EXPECT_TRUE(args2.IsValid()) << args2;
@@ -84,5 +90,14 @@ TEST(BeginFrameArgsTest, Create) {
   EXPECT_EQ(BeginFrameArgs::NORMAL, args2.type) << args2;
 }
 
+#ifndef NDEBUG
+TEST(BeginFrameArgsTest, Location) {
+  tracked_objects::Location expected_location = BEGINFRAME_FROM_HERE;
+
+  BeginFrameArgs args = CreateBeginFrameArgsForTesting(expected_location);
+  EXPECT_EQ(expected_location.ToString(), args.created_from.ToString());
+}
+#endif
+
 }  // namespace
 }  // namespace cc