[tracing] Introduce MemoryDumpArgs to enable light and heavy dumps

base/trace_event/trace_log.cc

Index: base/trace_event/trace_log.cc
diff --git a/base/trace_event/trace_log.cc b/base/trace_event/trace_log.cc
index 303f9db99e1030797f67e03ac37489ed087e8e11..56c01c1d610a695d086dc55cbbd4ba47812dcb18 100644
--- a/base/trace_event/trace_log.cc
+++ b/base/trace_event/trace_log.cc
@@ -227,7 +227,8 @@ class TraceLog::ThreadLocalEventBuffer
   void WillDestroyCurrentMessageLoop() override;
 
   // MemoryDumpProvider implementation.
-  bool OnMemoryDump(ProcessMemoryDump* pmd) override;
+  bool OnMemoryDump(const MemoryDumpArgs& args,
+                    ProcessMemoryDump* pmd) override;
 
   void FlushWhileLocked();
 
@@ -355,7 +356,8 @@ void TraceLog::ThreadLocalEventBuffer::WillDestroyCurrentMessageLoop() {
   delete this;
 }
 
-bool TraceLog::ThreadLocalEventBuffer::OnMemoryDump(ProcessMemoryDump* pmd) {
+bool TraceLog::ThreadLocalEventBuffer::OnMemoryDump(const MemoryDumpArgs& args,
+                                                    ProcessMemoryDump* pmd) {
   if (!chunk_)
     return true;
   std::string dump_base_name = StringPrintf(
@@ -466,7 +468,10 @@ void TraceLog::InitializeThreadLocalEventBufferIfSupported() {
   }
 }
 
-bool TraceLog::OnMemoryDump(ProcessMemoryDump* pmd) {
+bool TraceLog::OnMemoryDump(const MemoryDumpArgs& args,
+                            ProcessMemoryDump* pmd) {
+  // TODO(ssid): Use MemoryDumpArgs to create light dumps when requested

[petrcermak, 2015/07/31 13:23:01]

nit: Not sure whether we will have light tracing dumps because they would cause
less precise results overall.

[ssid, 2015/07/31 15:14:33]

That is true, the data collected is going to be complete for this, but then not
all the details about the tracing needs to be dumps. Just dumping the totals
would be sufficient here.

+  // (crbug.com/499731).
   TraceEventMemoryOverhead overhead;
   overhead.Add("TraceLog", sizeof(*this));
   {