tracing: get rid of files in TracingController interface

The only way to get the tracing data used to be by reading the file
provided in TracingController::DisableTracing() interface. This does
not fit well for most usages, so this introduces a TraceDataSink
interface that is backed either by a file, string, or, in case of
DevTools, by the protocol client.

This resolves the OOM in browser and imporves performance while
recording very large traces through DevTools, streamlines
TracingController core and reduces coplexity of code for most
TracingController clients.

BUG=409733,361045

Review URL: https://codereview.chromium.org/541763002

Cr-Commit-Position: refs/heads/master@{#294801}

2 files changed, 7 insertions, 15 deletions

diff --git a/components/feedback/tracing_manager.cc b/components/feedback/tracing_manager.cc
index e2d77ec..bd7ca79 100644
--- a/components/feedback/tracing_manager.cc
+++ b/components/feedback/tracing_manager.cc
@@ -5,14 +5,13 @@
 #include "components/feedback/tracing_manager.h"
 
 #include "base/bind.h"
-#include "base/files/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 {
+
 // Only once trace manager can exist at a time.
 TracingManager* g_tracing_manager = NULL;
 // Trace IDs start at 1 and increase.
@@ -43,9 +42,9 @@ 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()));
+      content::TracingController::CreateStringSink(
+          base::Bind(&TracingManager::OnTraceDataCollected,
+                     weak_ptr_factory_.GetWeakPtr())));
   return current_trace_id_;
 }
 
@@ -96,20 +95,13 @@ void TracingManager::StartTracing() {
       content::TracingController::EnableRecordingDoneCallback());
 }
 
-void TracingManager::OnTraceDataCollected(const base::FilePath& path) {
+void TracingManager::OnTraceDataCollected(base::RefCountedString* 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->data(), &output_val);
 
   scoped_refptr<base::RefCountedString> output(
       base::RefCountedString::TakeString(&output_val));
diff --git a/components/feedback/tracing_manager.h b/components/feedback/tracing_manager.h
index 1148a1c..e846f37 100644
--- a/components/feedback/tracing_manager.h
+++ b/components/feedback/tracing_manager.h
@@ -58,7 +58,7 @@ class TracingManager {
   TracingManager();
 
   void StartTracing();
-  void OnTraceDataCollected(const base::FilePath& path);
+  void OnTraceDataCollected(base::RefCountedString* data);
 
   // ID of the trace that is being collected.
   int current_trace_id_;