tracing: get rid of files in TracingController interface

components/feedback/tracing_manager.cc

 // 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 "components/feedback/tracing_manager.h"
 
 #include "base/bind.h"
-#include "base/file_util.h"
-#include "base/location.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "components/feedback/feedback_util.h"
 #include "content/public/browser/tracing_controller.h"
 
 namespace {
+
+class StringTraceDataSink : public content::TracingController::TraceDataSink {

[dsinclair, 2014/09/05 19:27:42]

Is this the same as the StringTraceDataSink in TracingControllerImpl? Can we
re-use that one?

+ public:
+  typedef base::Callback<void(const std::string&)> CompletionCallback;
+
+  explicit StringTraceDataSink(CompletionCallback callback)
+      : completion_callback_(callback) {
+  }
+
+  // TracingController::TraceDataSink implementation
+  virtual void AddTraceChunk(const std::string& chunk) OVERRIDE {
+    if (!trace_.empty())
+      trace_ += ",";
+    trace_ += chunk;
+  }
+  virtual void SetSystemTrace(const std::string& data) OVERRIDE {
+    system_trace_ = data;
+  }
+  virtual void Close() OVERRIDE {
+    std::string result = "{\"traceEvents\":[" + trace_ + "]";
+    if (!system_trace_.empty())
+      result += ",\"systemTraceEvents\":[" + system_trace_ + "]";
+    result += "}";
+
+    completion_callback_.Run(result);
+  }
+
+ private:
+  virtual ~StringTraceDataSink() {}
+
+  std::string trace_;
+  std::string system_trace_;
+  CompletionCallback completion_callback_;
+};
+
+
 // Only once trace manager can exist at a time.
 TracingManager* g_tracing_manager = NULL;
 // Trace IDs start at 1 and increase.
 int g_next_trace_id = 1;
 // Name of the file to store the tracing data as.
 const base::FilePath::CharType kTracingFilename[] =
     FILE_PATH_LITERAL("tracing.json");
 }
 
 TracingManager::TracingManager()
@@ skipping 10 matching lines @@
 }
 
 int TracingManager::RequestTrace() {
   // Return the current trace if one is being collected.
   if (current_trace_id_)
     return current_trace_id_;
 
   current_trace_id_ = g_next_trace_id;
   ++g_next_trace_id;
   content::TracingController::GetInstance()->DisableRecording(
-      base::FilePath(),
-      base::Bind(&TracingManager::OnTraceDataCollected,
-                 weak_ptr_factory_.GetWeakPtr()));
+      new StringTraceDataSink(base::Bind(&TracingManager::OnTraceDataCollected,
+                                         weak_ptr_factory_.GetWeakPtr())));
   return current_trace_id_;
 }
 
 bool TracingManager::GetTraceData(int id, const TraceDataCallback& callback) {
   // If a trace is being collected currently, send it via callback when
   // complete.
   if (current_trace_id_) {
     // Only allow one trace data request at a time.
     if (trace_callback_.is_null()) {
       trace_callback_ = callback;
@@ skipping 30 matching lines @@
   }
 }
 
 void TracingManager::StartTracing() {
   content::TracingController::GetInstance()->EnableRecording(
       base::debug::CategoryFilter(),
       base::debug::TraceOptions(),
       content::TracingController::EnableRecordingDoneCallback());
 }
 
-void TracingManager::OnTraceDataCollected(const base::FilePath& path) {
+void TracingManager::OnTraceDataCollected(const std::string& trace_data) {
   if (!current_trace_id_)
     return;
 
-  std::string data;
-  if (!base::ReadFileToString(path, &data)) {
-    LOG(ERROR) << "Failed to read trace data from: " << path.value();
-    return;
-  }
-  base::DeleteFile(path, false);
-
   std::string output_val;
   feedback_util::ZipString(
-      base::FilePath(kTracingFilename), data, &output_val);
+      base::FilePath(kTracingFilename), trace_data, &output_val);
 
   scoped_refptr<base::RefCountedString> output(
       base::RefCountedString::TakeString(&output_val));
 
   trace_data_[current_trace_id_] = output;
 
   if (!trace_callback_.is_null()) {
     trace_callback_.Run(output);
     trace_callback_.Reset();
   }
@@ skipping 11 matching lines @@
 // static
 scoped_ptr<TracingManager> TracingManager::Create() {
   if (g_tracing_manager)
     return scoped_ptr<TracingManager>();
   return scoped_ptr<TracingManager>(new TracingManager());
 }
 
 TracingManager* TracingManager::Get() {
   return g_tracing_manager;
 }