Adding blink gc memory dump infrastructure for thread specific dumps.

Source/platform/heap/ThreadState.h

Index: Source/platform/heap/ThreadState.h
diff --git a/Source/platform/heap/ThreadState.h b/Source/platform/heap/ThreadState.h
index 459b8acd854aa0178a933f85b33cea1ea8f0e366..276e3ed70f57eced2cefccf555b485022137928c 100644
--- a/Source/platform/heap/ThreadState.h
+++ b/Source/platform/heap/ThreadState.h
@@ -34,6 +34,7 @@
 #include "platform/PlatformExport.h"
 #include "platform/heap/AddressSanitizer.h"
 #include "platform/heap/ThreadingTraits.h"
+#include "public/platform/WebMemoryDumpProvider.h"
 #include "public/platform/WebThread.h"
 #include "wtf/Forward.h"
 #include "wtf/HashMap.h"
@@ -164,7 +165,7 @@ struct AgeCounts {
 typedef HashMap<String, AgeCounts> ClassAgeCountsMap;
 #endif
 
-class PLATFORM_EXPORT ThreadState {
+class PLATFORM_EXPORT ThreadState : public WebMemoryDumpProvider {

[Primiano Tucci (use gerrit), 2015/05/21 18:43:10]

We discussed this offline (there is a thread in the internal oilpan ML pending).
There seems to be one ThreadState per therad, but PostGC seems to be called once
on a single (probably main) thread, and scans all the threads.
As a consequence, having this as the dumper is odd because:
 - Will give the false expectation that the onMemoryDump is called on the same
Thread of this ThreadState, while that will not be the case.
 - Will end up register one dumper per thread, and it seems that we don't really
need it.

We should have an external dumper class (just one).
All the thread states should dumpInto a shared WebProcessMemoryDump (obtained
through the new API that is landing), and later on the dumper should just merge
(takeAllDumps()) that dump into the WPMD passed to onMemoryDump.
If my understandings of the oilpan threading model are correct, we can do this
by using just one extra WPMD, no locks, and no double-buffering.

[ssid, 2015/05/22 13:34:07]

Done.

     WTF_MAKE_NONCOPYABLE(ThreadState);
 public:
     // When garbage collecting we need to know whether or not there
@@ -457,6 +458,10 @@ public:
     // Visit all persistents allocated on this thread.
     void visitPersistents(Visitor*);
 
+    // Takes dump of memory statistics when tracing is enabled with memory
+    // category.
+    void dumpMemoryIfNecessary();

[Primiano Tucci (use gerrit), 2015/05/21 18:43:10]

Had a second thought about this, please don't hate me, I'm very terrible in
naming decisions.
How about dumpIfMemoryProfilingIsEnabled() ?
"necessary" is a bit generic :)
If you are not convinced, don't worry, probably in the next patchset I will
propose another different name :P

[ssid, 2015/05/22 13:34:07]

Haha now there is no need to think about it. :) Peace

+
 #if ENABLE(GC_PROFILING)
     const GCInfo* findGCInfo(Address);
     static const GCInfo* findGCInfoFromAllThreads(Address);
@@ -609,6 +614,9 @@ public:
     void allocationPointAdjusted(int heapIndex);
     void promptlyFreed(size_t gcInfoIndex);
 
+    // WebMemoryDumpProvider implementation.
+    bool onMemoryDump(WebProcessMemoryDump*) override;

[Primiano Tucci (use gerrit), 2015/05/21 18:43:10]

This should go away from here, as per discussion up.

[ssid, 2015/05/22 13:34:07]

Done.

+
 private:
     ThreadState();
     ~ThreadState();
@@ -706,6 +714,8 @@ private:
 
     Vector<PageMemoryRegion*> m_allocatedRegionsSinceLastGC;
 
+    OwnPtr<WebProcessMemoryDump> m_lastProcessMemoryDump;

[Primiano Tucci (use gerrit), 2015/05/21 18:43:10]

And this should be just one, shared by all the ThreadState(s).

[ssid, 2015/05/22 13:34:07]

Done.

+
 #if ENABLE(GC_PROFILING)
     double m_nextFreeListSnapshotTime;
 #endif