arc: enable Android tracing from chrome://tracing in dev mode

chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.cc

+// 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 "chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "components/arc/arc_bridge_service.h"
+#include "components/arc/arc_service_manager.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace arc {
+
+namespace {
+
+// The prefix of the categories to be shown on the trace selection UI.
+// The space at the end of the string is intentional as the separator between
+// the prefix and the real categories.
+constexpr char kCategoryPrefix[] = TRACE_DISABLED_BY_DEFAULT("android ");
+
+}  // namespace
+
+ArcTracingBridge::ArcTracingBridge(ArcBridgeService* bridge_service)
+    : ArcService(bridge_service), weak_ptr_factory_(this) {
+  arc_bridge_service()->tracing()->AddObserver(this);
+  chromeos::ArcTracingAgent::GetInstance()->SetDelegate(this);
+}
+
+ArcTracingBridge::~ArcTracingBridge() {
+  chromeos::ArcTracingAgent::GetInstance()->SetDelegate(nullptr);
+  arc_bridge_service()->tracing()->RemoveObserver(this);
+}
+
+void ArcTracingBridge::OnInstanceReady() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  mojom::TracingInstance* tracing_instance = ARC_GET_INSTANCE_FOR_METHOD(
+      arc_bridge_service()->tracing(), QueryAvailableCategories);
+  if (!tracing_instance)
+    return;
+  tracing_instance->QueryAvailableCategories(base::Bind(
+      &ArcTracingBridge::OnCategoriesReady, weak_ptr_factory_.GetWeakPtr()));
+}
+
+void ArcTracingBridge::OnCategoriesReady(
+    const std::vector<std::string>& categories) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  // There is no API in TraceLog to remove a category from the UI. As an
+  // alternative, the old category that is no longer in |categories_| will be
+  // ignored when calling |StartTracing|.
+  categories_.clear();
+  for (const auto& category : categories) {
+    categories_.push_back(Category{category, kCategoryPrefix + category});

[dcheng, 2017/03/10 22:09:24]

Nit: Omit Category (that way it's clear this isn't a ctor)

[Earl Ou, 2017/03/13 02:00:13]

Done.

+    // Show the category name in the selection UI.
+    base::trace_event::TraceLog::GetCategoryGroupEnabled(
+        categories_.back().full_name.c_str());
+  }
+}
+
+void ArcTracingBridge::StartTracing(
+    const base::trace_event::TraceConfig& trace_config,
+    const StartTracingCallback& callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  mojom::TracingInstance* tracing_instance = ARC_GET_INSTANCE_FOR_METHOD(
+      arc_bridge_service()->tracing(), StartTracing);
+  if (!tracing_instance) {
+    // Use PostTask as the convention of TracingAgent. The caller expects
+    // callback to be called after this function returns.
+    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                  base::Bind(callback, false));
+    return;
+  }
+
+  std::vector<std::string> selected_categories;
+  for (const auto& category : categories_) {
+    if (trace_config.IsCategoryGroupEnabled(category.full_name.c_str()))
+      selected_categories.push_back(category.name);
+  }
+
+  tracing_instance->StartTracing(selected_categories, callback);
+}
+
+void ArcTracingBridge::StopTracing(const StopTracingCallback& callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  mojom::TracingInstance* tracing_instance =
+      ARC_GET_INSTANCE_FOR_METHOD(arc_bridge_service()->tracing(), StopTracing);
+  if (!tracing_instance) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                  base::Bind(callback, false));
+    return;
+  }
+  tracing_instance->StopTracing(callback);
+}
+
+}  // namespace arc