Binds two IDs together.

This macro provides a mechanism to tell trace consumers
that two different IDs are actually identical and they
refer to the same thing.

For more context:
https://docs.google.com/a/google.com/document/d/1s0DKjNJk85hDuRp5IqujwZvPML-MPsyAtDeksMwBw7s/edit?usp=sharing

BUG=catapult:#2465

Review-Url: https://codereview.chromium.org/2142023003
Cr-Commit-Position: refs/heads/master@{#406648}

base/trace_event/common/trace_event_common.h

@@ -1001,6 +1001,17 @@
   INTERNAL_TRACE_EVENT_SCOPED_CONTEXT(category_group, name,       \
                                       TRACE_ID_DONT_MANGLE(context))
 
+// Macro to specify that two trace IDs are identical. For example,
+// TRACE_BIND_IDS(
+//     "category", "name",
+//     TRACE_ID_WITH_SCOPE("net::URLRequest", 0x1000),
+//     TRACE_ID_WITH_SCOPE("blink::ResourceFetcher::FetchRequest", 0x2000))
+// tells the trace consumer that events with ID ("net::URLRequest", 0x1000) from
+// the current process have the same ID as events with ID
+// ("blink::ResourceFetcher::FetchRequest", 0x2000).
+#define TRACE_BIND_IDS(category_group, name, id, bind_id) \
+  INTERNAL_TRACE_EVENT_ADD_BIND_IDS(category_group, name, id, bind_id);
+
 // Macro to efficiently determine if a given category group is enabled.
 #define TRACE_EVENT_CATEGORY_GROUP_ENABLED(category_group, ret)             \
   do {                                                                      \
@@ -1066,6 +1077,7 @@
 #define TRACE_EVENT_PHASE_CLOCK_SYNC ('c')
 #define TRACE_EVENT_PHASE_ENTER_CONTEXT ('(')
 #define TRACE_EVENT_PHASE_LEAVE_CONTEXT (')')
+#define TRACE_EVENT_PHASE_BIND_IDS ('=')
 
 // Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
 #define TRACE_EVENT_FLAG_NONE (static_cast<unsigned int>(0))

base/trace_event/trace_event.h

@@ -349,6 +349,31 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
     }                                                                         \
   } while (0)
 
+// The trace ID and bind ID will never be mangled by this macro.
+#define INTERNAL_TRACE_EVENT_ADD_BIND_IDS(category_group, name, id, bind_id,  \
+                                          ...)                                \
+    do {                                                                      \
+      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                 \
+      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
+        trace_event_internal::TraceID::DontMangle source_id(id);              \
+        trace_event_internal::TraceID::DontMangle target_id(bind_id);         \
+        if (target_id.scope() == trace_event_internal::kGlobalScope) {        \
+          trace_event_internal::AddTraceEvent(                                \
+              TRACE_EVENT_PHASE_BIND_IDS,                                     \
+              INTERNAL_TRACE_EVENT_UID(category_group_enabled),               \
+              name, source_id.scope(), source_id.raw_id(),                    \
+              TRACE_EVENT_FLAG_HAS_ID, target_id.raw_id(), ##__VA_ARGS__);    \
+        } else {                                                              \
+          trace_event_internal::AddTraceEvent(                                \
+              TRACE_EVENT_PHASE_BIND_IDS,                                     \
+              INTERNAL_TRACE_EVENT_UID(category_group_enabled),               \
+              name, source_id.scope(), source_id.raw_id(),                    \
+              TRACE_EVENT_FLAG_HAS_ID, target_id.raw_id(),                    \
+              "bind_scope", target_id.scope(), ##__VA_ARGS__);                \
+        }                                                                     \
+      }                                                                       \
+    } while (0)
+
 // Implementation detail: internal macro to create static category and add
 // metadata event if the category is enabled.
 #define INTERNAL_TRACE_EVENT_METADATA_ADD(category_group, name, ...)        \

base/trace_event/trace_event_impl.cc

@@ -368,7 +368,8 @@ void TraceEvent::AppendAsJSON(
     StringAppendF(out, ",\"bp\":\"e\"");
 
   if ((flags_ & TRACE_EVENT_FLAG_FLOW_OUT) ||
-      (flags_ & TRACE_EVENT_FLAG_FLOW_IN)) {
+      (flags_ & TRACE_EVENT_FLAG_FLOW_IN) ||
+      phase_ == TRACE_EVENT_PHASE_BIND_IDS) {
     StringAppendF(out, ",\"bind_id\":\"0x%" PRIx64 "\"",
                   static_cast<uint64_t>(bind_id_));
   }

base/trace_event/trace_event_unittest.cc

@@ -517,6 +517,11 @@ void TraceWithAllMacroVariants(WaitableEvent* task_complete_event) {
                                context_id);
     TRACE_EVENT_SCOPED_CONTEXT("all", "TRACE_EVENT_SCOPED_CONTEXT call",
                                context_id);
+
+    TRACE_BIND_IDS("all", "TRACE_BIND_IDS simple call", 0x1000, 0x2000);
+    TRACE_BIND_IDS("all", "TRACE_BIND_IDS scoped call",
+                   TRACE_ID_WITH_SCOPE("scope 1", 0x1000),
+                   TRACE_ID_WITH_SCOPE("scope 2", 0x2000));
   }  // Scope close causes TRACE_EVENT0 etc to send their END events.
 
   if (task_complete_event)
@@ -957,6 +962,45 @@ void ValidateAllTraceMacrosCreatedData(const ListValue& trace_parsed) {
     EXPECT_TRUE((item && item->GetString("id", &id)));
     EXPECT_EQ("0x20151021", id);
   }
+
+  EXPECT_FIND_("TRACE_BIND_IDS simple call");
+  {
+    std::string ph;
+    EXPECT_TRUE((item && item->GetString("ph", &ph)));
+    EXPECT_EQ("=", ph);
+
+    EXPECT_FALSE((item && item->HasKey("scope")));
+    std::string id;
+    EXPECT_TRUE((item && item->GetString("id", &id)));
+    EXPECT_EQ("0x1000", id);
+
+    EXPECT_FALSE((item && item->HasKey("args.bind_scope")));
+    std::string bind_id;
+    EXPECT_TRUE((item && item->GetString("bind_id", &id)));
+    EXPECT_EQ("0x2000", id);
+  }
+
+  EXPECT_FIND_("TRACE_BIND_IDS scoped call");
+  {
+    std::string ph;
+    EXPECT_TRUE((item && item->GetString("ph", &ph)));
+    EXPECT_EQ("=", ph);
+
+    std::string id_scope;
+    EXPECT_TRUE((item && item->GetString("scope", &id_scope)));
+    EXPECT_EQ("scope 1", id_scope);
+    std::string id;
+    EXPECT_TRUE((item && item->GetString("id", &id)));
+    EXPECT_EQ("0x1000", id);
+
+    std::string bind_scope;
+    EXPECT_TRUE((item && item->GetString("args.bind_scope", &bind_scope)));
+    EXPECT_EQ("scope 2", bind_scope);
+    std::string bind_id;
+    EXPECT_TRUE((item && item->GetString("bind_id", &id)));
+    EXPECT_EQ("0x2000", id);
+  }
+
 }
 
 void TraceManyInstantEvents(int thread_id, int num_events,