[tracing] Introduce MemoryDumpArgs to enable light and heavy dumps

gin/v8_isolate_memory_dump_provider.cc

Index: gin/v8_isolate_memory_dump_provider.cc
diff --git a/gin/v8_isolate_memory_dump_provider.cc b/gin/v8_isolate_memory_dump_provider.cc
index 28a05ecbcb5a994915ede3968bb496bd5719d029..2d261eb9ecc1d26f5cf8d6a88f9dfc238e71a572 100644
--- a/gin/v8_isolate_memory_dump_provider.cc
+++ b/gin/v8_isolate_memory_dump_provider.cc
@@ -28,7 +28,11 @@ V8IsolateMemoryDumpProvider::~V8IsolateMemoryDumpProvider() {
 // Called at trace dump point time. Creates a snapshot with the memory counters
 // for the current isolate.
 bool V8IsolateMemoryDumpProvider::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
     base::trace_event::ProcessMemoryDump* process_memory_dump) {
+  // TODO(ssid): Use MemoryDumpArgs to create light dumps when requested

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

Why do you put this comment into some dump providers (e.g. tracing, v8) and not
others (e.g. malloc, winheap)?

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

I did not put in other dump providers since they do not need a difference
between light and heavy, since it is already light. I did not want to add a
comment saying they don't need light dumps since, if we add more args in future
this would mean that we need to keep updating the comment.

+  // (crbug.com/499731).
+
   if (isolate_holder_->access_mode() == IsolateHolder::kUseLocker) {
     v8::Locker locked(isolate_holder_->isolate());
     DumpHeapStatistics(process_memory_dump);