tracing: get rid of files in TracingController interface

components/feedback/tracing_manager.cc

Index: components/feedback/tracing_manager.cc
diff --git a/components/feedback/tracing_manager.cc b/components/feedback/tracing_manager.cc
index f35fe80876f44763eee829050efbe73d4febb7b0..4539a9a1265abe7f5869b023ab71298174ea5bfa 100644
--- a/components/feedback/tracing_manager.cc
+++ b/components/feedback/tracing_manager.cc
@@ -5,14 +5,49 @@
 #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 {
+ 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);
+    delete this;
+  }
+
+ 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.
@@ -43,9 +78,8 @@ int TracingManager::RequestTrace() {
   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_;
 }
 
@@ -96,20 +130,13 @@ void TracingManager::StartTracing() {
       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));