DevTools: add Tracing agent on back-end

Source/core/inspector/InspectorTracingAgent.cpp

+/*
+ * Copyright 2014 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 "config.h"
+
+#include "core/inspector/InspectorTracingAgent.h"
+
+#include "core/inspector/IdentifiersFactory.h"
+#include "core/inspector/InspectorClient.h"
+#include "core/inspector/InspectorState.h"
+#include "platform/TraceEvent.h"
+
+namespace WebCore {
+
+namespace TracingAgentState {
+const char enabled[] = "enabled";
+const char sessionId[] = "sessionId";
+const char tracingCategoryFilter[] = "tracingCategoryFilter";
+}
+
+InspectorTracingAgent::InspectorTracingAgent(InspectorClient* client)
+    : InspectorBaseAgent<InspectorTracingAgent>("Tracing")
+    , m_frontend(0)
+    , m_client(client)
+    , m_shouldStopTracing(false)
+    , m_layerTreeId(0)
+{
+}
+
+void InspectorTracingAgent::setFrontend(InspectorFrontend* frontend)
+{
+    m_frontend = frontend->tracing();
+}
+
+void InspectorTracingAgent::clearFrontend()
+{
+    ErrorString unused;
+    disable(&unused);
+    m_frontend = 0;
+}
+
+void InspectorTracingAgent::restore()
+{
+    emitMetadataEvents();
+}
+
+void InspectorTracingAgent::enable(ErrorString*, const String& categoryFilter)
+{
+    m_state->setBoolean(TracingAgentState::enabled, true);
+    m_state->setString(TracingAgentState::tracingCategoryFilter, categoryFilter);
+}
+
+void InspectorTracingAgent::disable(ErrorString*)
+{
+    m_state->setBoolean(TracingAgentState::enabled, false);
+}
+
+void InspectorTracingAgent::start(ErrorString*, const String&, const String&, const double*)
+{
+    innerStart();
+}
+
+void InspectorTracingAgent::startFromBackend()
+{
+    if (!m_state->getBoolean(TracingAgentState::enabled)) {
+        m_shouldStopTracing = false;
+        return;
+    }
+    m_shouldStopTracing = true;
+    String tracingCategoryFilter = m_state->getString(TracingAgentState::tracingCategoryFilter);
+    m_client->enableTracing(tracingCategoryFilter);
+    innerStart();
+}
+
+void InspectorTracingAgent::endFromBackend()
+{
+    if (!m_shouldStopTracing)
+        return;
+    m_shouldStopTracing = true;
+    m_client->disableTracing();
+}
+
+
+void InspectorTracingAgent::innerStart()
+{
+    String sessionId = IdentifiersFactory::createIdentifier();
+    m_state->setString(TracingAgentState::sessionId, sessionId);
+    m_frontend->pageTracingStarted(sessionId);

[yurys, 2014/04/24 14:08:09]

I believe we should use separate events to notify front-end that tracing
started/stopped by the user code. Using the same event for
console.profile/profileEnd and front-end initiated profiles proved to be
difficult to maintain and we eventually introduced separate events for
console.profile/profileEnd.

+    emitMetadataEvents();
+}
+
+String InspectorTracingAgent::sessionId()
+{
+    return m_state->getString(TracingAgentState::sessionId);
+}
+
+const char devtoolsMetadataEventCategory[] = TRACE_DISABLED_BY_DEFAULT("devtools.timeline");
+
+void InspectorTracingAgent::emitMetadataEvents()
+{
+    TRACE_EVENT_INSTANT1(devtoolsMetadataEventCategory, "TracingStartedInPage", "sessionId", sessionId().utf8());
+    if (m_layerTreeId)
+        setLayerTreeId(m_layerTreeId);
+}
+
+void InspectorTracingAgent::setLayerTreeId(int layerTreeId)
+{
+    m_layerTreeId = layerTreeId;
+    TRACE_EVENT_INSTANT2(devtoolsMetadataEventCategory, "SetLayerTreeId", "sessionId", sessionId().utf8(), "layerTreeId", m_layerTreeId);
+}
+
+}