Revert of Revert "Revert 237280 "Remove TraceController""

chrome/test/automation/automation_proxy.cc

Index: chrome/test/automation/automation_proxy.cc
diff --git a/chrome/test/automation/automation_proxy.cc b/chrome/test/automation/automation_proxy.cc
index aae6691b5b025ce5337948d3fd430b9b25243a94..1c8cdb233b4af2e63c5ca2b927200d4ecc45305f 100644
--- a/chrome/test/automation/automation_proxy.cc
+++ b/chrome/test/automation/automation_proxy.cc
@@ -7,7 +7,7 @@
 #include <sstream>
 
 #include "base/basictypes.h"
-#include "base/file_util.h"
+#include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/waitable_event.h"
@@ -410,13 +410,31 @@
 
 bool AutomationProxy::EndTracing(std::string* json_trace_output) {
   bool success = false;
-  base::FilePath path;
-  if (!Send(new AutomationMsg_EndTracing(&path, &success)) || !success)
-    return false;
-
-  bool ok = base::ReadFileToString(path, json_trace_output);
-  DCHECK(ok);
-  base::DeleteFile(path, false);
+  size_t num_trace_chunks = 0;
+  if (!Send(new AutomationMsg_EndTracing(&num_trace_chunks, &success)) ||
+      !success)
+    return false;
+
+  std::string chunk;
+  base::debug::TraceResultBuffer buffer;
+  base::debug::TraceResultBuffer::SimpleOutput output;
+  buffer.SetOutputCallback(output.GetCallback());
+
+  // TODO(jbates): See bug 100255, IPC send fails if message is too big. This
+  // code can be simplified if that limitation is fixed.
+  // Workaround IPC payload size limitation by getting chunks.
+  buffer.Start();
+  for (size_t i = 0; i < num_trace_chunks; ++i) {
+    // The broswer side AutomationProvider resets state at BeginTracing,
+    // so it can recover even after this fails mid-way.
+    if (!Send(new AutomationMsg_GetTracingOutput(&chunk, &success)) ||
+        !success)
+      return false;
+    buffer.AddFragment(chunk);
+  }
+  buffer.Finish();
+
+  *json_trace_output = output.json_output;
   return true;
 }