[DevTools] Do not plumb TraceLog::SetEnabled through content

Blink can now do it directly, which unblocks moving DevToolsAgent
to blink.

Bug: 776009
Change-Id: I4b1466005b10dd9969040803a9517e6dff18dc38
Reviewed-on: https://chromium-review.googlesource.com/827551Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524476}

content/renderer/devtools/devtools_agent.cc

@@ -13,7 +13,6 @@
 #include "base/lazy_instance.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
-#include "base/trace_event/trace_event.h"
 #include "content/child/child_process.h"
 #include "content/common/devtools_messages.h"
 #include "content/common/frame_messages.h"
@@ -241,23 +240,6 @@ bool DevToolsAgent::RequestDevToolsForFrame(int session_id,
   return true;
 }
 
-void DevToolsAgent::EnableTracing(const WebString& category_filter) {
-  // Tracing is already started by DevTools TracingHandler::Start for the
-  // renderer target in the browser process. It will eventually start tracing in
-  // the renderer process via IPC. But we still need a redundant
-  // TraceLog::SetEnabled call here for
-  // InspectorTracingAgent::emitMetadataEvents(), at which point, we are not
-  // sure if tracing is already started in the renderer process.
-  TraceLog* trace_log = TraceLog::GetInstance();
-  trace_log->SetEnabled(
-      base::trace_event::TraceConfig(category_filter.Utf8(), ""),
-      TraceLog::RECORDING_MODE);
-}
-
-void DevToolsAgent::DisableTracing() {
-  TraceLog::GetInstance()->SetDisabled();
-}
-
 void DevToolsAgent::SetCPUThrottlingRate(double rate) {
   DevToolsCPUThrottler::GetInstance()->SetThrottlingRate(rate);
 }

content/renderer/devtools/devtools_agent.h

@@ -70,8 +70,6 @@ class CONTENT_EXPORT DevToolsAgent : public RenderFrameObserver,
   void DidExitDebugLoop() override;
   bool RequestDevToolsForFrame(int session_id,
                                blink::WebLocalFrame* frame) override;
-  void EnableTracing(const blink::WebString& category_filter) override;
-  void DisableTracing() override;
   void SetCPUThrottlingRate(double rate) override;
 
   void DetachSession(int session_id);

third_party/WebKit/Source/core/exported/WebDevToolsAgentImpl.cpp

@@ -468,16 +468,6 @@ void WebDevToolsAgentImpl::LayerTreeViewChanged(
     it.value->SetLayerTreeId(layer_tree_id_);
 }
 
-void WebDevToolsAgentImpl::EnableTracing(const String& category_filter) {
-  if (client_)
-    client_->EnableTracing(category_filter);
-}
-
-void WebDevToolsAgentImpl::DisableTracing() {
-  if (client_)
-    client_->DisableTracing();
-}
-
 void WebDevToolsAgentImpl::ShowReloadingBlanket() {
   for (auto& it : overlay_agents_)
     it.value->ShowReloadingBlanket();

third_party/WebKit/Source/core/exported/WebDevToolsAgentImpl.h

@@ -108,8 +108,6 @@ class CORE_EXPORT WebDevToolsAgentImpl final
                        bool include_view_agents);
 
   // InspectorTracingAgent::Client implementation.
-  void EnableTracing(const WTF::String& category_filter) override;
-  void DisableTracing() override;
   void ShowReloadingBlanket() override;
   void HideReloadingBlanket() override;
 

third_party/WebKit/Source/core/inspector/InspectorTracingAgent.cpp

@@ -75,13 +75,20 @@ void InspectorTracingAgent::start(Maybe<String> categories,
   instrumenting_agents_->addInspectorTracingAgent(this);
   state_->setString(TracingAgentState::kSessionId,
                     IdentifiersFactory::CreateIdentifier());
-  client_->EnableTracing(categories.fromMaybe(String()));
+
+  // Tracing is already started by DevTools TracingHandler::Start for the
+  // renderer target in the browser process. It will eventually start tracing
+  // in the renderer process via IPC. But we still need a redundant enable here
+  // for EmitMetadataEvents, at which point we are not sure if tracing
+  // is already started in the renderer process.
+  TraceEvent::EnableTracing(categories.fromMaybe(String()));
+
   EmitMetadataEvents();
   callback->sendSuccess();
 }
 
 void InspectorTracingAgent::end(std::unique_ptr<EndCallback> callback) {
-  client_->DisableTracing();
+  TraceEvent::DisableTracing();
   InnerDisable();
   callback->sendSuccess();
 }

third_party/WebKit/Source/core/inspector/InspectorTracingAgent.h

@@ -26,8 +26,6 @@ class CORE_EXPORT InspectorTracingAgent final
    public:
     virtual ~Client() {}
 
-    virtual void EnableTracing(const String& category_filter) = 0;
-    virtual void DisableTracing() = 0;
     virtual void ShowReloadingBlanket() = 0;
     virtual void HideReloadingBlanket() = 0;
   };

third_party/WebKit/Source/platform/instrumentation/BUILD.gn

@@ -15,6 +15,7 @@ jumbo_source_set("instrumentation") {
     "resource_coordinator/RendererResourceCoordinator.h",
     "tracing/MemoryCacheDumpProvider.cpp",
     "tracing/MemoryCacheDumpProvider.h",
+    "tracing/TraceEvent.cpp",
     "tracing/TraceEvent.h",
     "tracing/TracedValue.cpp",
     "tracing/TracedValue.h",

third_party/WebKit/Source/platform/instrumentation/tracing/TraceEvent.cpp

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "platform/instrumentation/tracing/TraceEvent.h"
+
+#include "base/trace_event/trace_event.h"
+
+namespace blink {
+namespace TraceEvent {
+
+void EnableTracing(const String& category_filter) {
+  base::trace_event::TraceLog::GetInstance()->SetEnabled(
+      base::trace_event::TraceConfig(category_filter.Utf8().data(), ""),
+      base::trace_event::TraceLog::RECORDING_MODE);
+}
+
+void DisableTracing() {
+  base::trace_event::TraceLog::GetInstance()->SetDisabled();
+}
+
+}  // namespace TraceEvent
+}  // namespace blink

third_party/WebKit/Source/platform/instrumentation/tracing/TraceEvent.h

@@ -7,7 +7,9 @@
 
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
+#include "platform/PlatformExport.h"
 #include "platform/wtf/text/CString.h"
+#include "platform/wtf/text/WTFString.h"
 
 namespace WTF {
 
@@ -35,6 +37,9 @@ inline base::TimeTicks ToTraceTimestamp(double seconds) {
 // This is to avoid error of passing a chromium time internal value.
 void ToTraceTimestamp(int64_t);
 
+PLATFORM_EXPORT void EnableTracing(const String& category_filter);
+PLATFORM_EXPORT void DisableTracing();
+
 }  // namespace TraceEvent
 }  // namespace blink
 

third_party/WebKit/public/web/WebDevToolsAgentClient.h

@@ -66,9 +66,6 @@ class WebDevToolsAgentClient {
     return false;
   }
 
-  virtual void EnableTracing(const WebString& category_filter) {}
-  virtual void DisableTracing() {}
-
   virtual void SetCPUThrottlingRate(double rate) {}
 
  protected: