Add support to create memory allocator dump in base::DiscardableMemory

content/common/discardable_shared_memory_heap.cc

Index: content/common/discardable_shared_memory_heap.cc
diff --git a/content/common/discardable_shared_memory_heap.cc b/content/common/discardable_shared_memory_heap.cc
index 958fa82554efecf5d9c4dee25bb6206cf7e891c9..604d6edaf78f8d08d042f7bcd8530ae58bf58d95 100644
--- a/content/common/discardable_shared_memory_heap.cc
+++ b/content/common/discardable_shared_memory_heap.cc
@@ -60,6 +60,27 @@ bool DiscardableSharedMemoryHeap::ScopedMemorySegment::IsResident() const {
   return heap_->IsMemoryResident(shared_memory_.get());
 }
 
+bool DiscardableSharedMemoryHeap::ScopedMemorySegment::ContainsSpan(
+    Span* span) const {
+  return shared_memory_ == span->shared_memory();
+}
+
+base::trace_event::MemoryAllocatorDump*
+DiscardableSharedMemoryHeap::ScopedMemorySegment::CreateMemoryAllocatorDump(
+    Span* span,
+    const char* name,
+    base::trace_event::ProcessMemoryDump* pmd) const {
+  DCHECK_EQ(shared_memory_, span->shared_memory());
+  base::trace_event::MemoryAllocatorDump* dump = pmd->CreateAllocatorDump(name);
+  dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                  base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                  static_cast<uint64_t>(span->length()));
+
+  pmd->AddSuballocation(dump->guid(),
+                        base::StringPrintf("discardable/segment_%d", id_));
+  return dump;
+}
+
 void DiscardableSharedMemoryHeap::ScopedMemorySegment::OnMemoryDump(
     base::trace_event::ProcessMemoryDump* pmd) const {
   heap_->OnMemoryDump(shared_memory_.get(), size_, id_, pmd);
@@ -398,4 +419,30 @@ DiscardableSharedMemoryHeap::GetSegmentGUIDForTracing(uint64 tracing_process_id,
       "discardable-x-process/%" PRIx64 "/%d", tracing_process_id, segment_id));
 }
 
+base::trace_event::MemoryAllocatorDump*
+DiscardableSharedMemoryHeap::CreateMemoryAllocatorDump(
+    Span* span,
+    const char* name,
+    base::trace_event::ProcessMemoryDump* pmd) const {
+  if (!span->shared_memory()) {
+    base::trace_event::MemoryAllocatorDump* dump =
+        pmd->CreateAllocatorDump(name);
+    dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                    base::trace_event::MemoryAllocatorDump::kUnitsBytes, 0u);
+    return dump;
+  }
+
+  base::trace_event::MemoryAllocatorDump* allocator_dump;
+  std::for_each(

[reveman, 2015/08/24 16:50:06]

can you use find_if instead? I think that represents the intent better and is
easier to understand.

[ssid, 2015/08/24 17:21:13]

Done.

+      memory_segments_.begin(), memory_segments_.end(),
+      [span, name, pmd, &allocator_dump](const ScopedMemorySegment* segment) {
+        if (segment->ContainsSpan(span))
+          allocator_dump = segment->CreateMemoryAllocatorDump(span, name, pmd);
+      });
+
+  // Span with a shared memory should be found in some segment.
+  DCHECK(allocator_dump != nullptr);

[reveman, 2015/08/24 16:50:06]

nit: DCHECK(!allocator_dump)

though this doesn't work right now as allocator_dump is not initialized to null.

[ssid, 2015/08/24 17:21:13]

Done.

+  return allocator_dump;
+}
+
 }  // namespace content