[tracing] Display the locked size of discardable memory segment.

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 ccf2729c557f660e3b675def1393449be60564dd..b641c0697442579e09a4b2801beca411f05540e3 100644
--- a/content/common/discardable_shared_memory_heap.cc
+++ b/content/common/discardable_shared_memory_heap.cc
@@ -28,8 +28,10 @@ DiscardableSharedMemoryHeap::Span::Span(
     base::DiscardableSharedMemory* shared_memory,
     size_t start,
     size_t length)
-    : shared_memory_(shared_memory), start_(start), length_(length) {
-}
+    : shared_memory_(shared_memory),
+      start_(start),
+      length_(length),
+      is_locked_(false) {}
 
 DiscardableSharedMemoryHeap::Span::~Span() {
 }
@@ -278,6 +280,7 @@ DiscardableSharedMemoryHeap::Carve(Span* span, size_t blocks) {
   if (extra) {
     scoped_ptr<Span> leftover(
         new Span(serving->shared_memory_, serving->start_ + blocks, extra));
+    leftover->set_is_locked(false);
     DCHECK_IMPLIES(extra > 1, spans_.find(leftover->start_) == spans_.end());
     RegisterSpan(leftover.get());
 
@@ -366,18 +369,23 @@ void DiscardableSharedMemoryHeap::OnMemoryDump(
     int32_t segment_id,
     base::trace_event::ProcessMemoryDump* pmd) {
   size_t allocated_objects_count = 0;
-  size_t allocated_objects_size_in_bytes = 0;
+  size_t allocated_objects_blocks = 0;
+  size_t locked_objects_blocks = 0;
   size_t offset =
       reinterpret_cast<size_t>(shared_memory->memory()) / block_size_;
   size_t end = offset + size / block_size_;
   while (offset < end) {
     Span* span = spans_[offset];
     if (!IsInFreeList(span)) {
+      allocated_objects_blocks += span->length_;
+      locked_objects_blocks += span->is_locked_ ? span->length_ : 0;
       allocated_objects_count++;
-      allocated_objects_size_in_bytes += span->length_ * block_size_;
     }
     offset += span->length_;
   }
+  size_t allocated_objects_size_in_bytes =
+      allocated_objects_blocks * block_size_;
+  size_t locked_objects_size_in_bytes = locked_objects_blocks * block_size_;
 
   std::string segment_dump_name =
       base::StringPrintf("discardable/segment_%d", segment_id);
@@ -385,16 +393,19 @@ void DiscardableSharedMemoryHeap::OnMemoryDump(
       pmd->CreateAllocatorDump(segment_dump_name);
   segment_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                           base::trace_event::MemoryAllocatorDump::kUnitsBytes,
-                          static_cast<uint64_t>(size));
+                          size);
 
   base::trace_event::MemoryAllocatorDump* obj_dump =
       pmd->CreateAllocatorDump(segment_dump_name + "/allocated_objects");
   obj_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameObjectCount,
                       base::trace_event::MemoryAllocatorDump::kUnitsObjects,
-                      static_cast<uint64_t>(allocated_objects_count));
+                      allocated_objects_count);
   obj_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                       base::trace_event::MemoryAllocatorDump::kUnitsBytes,
-                      static_cast<uint64_t>(allocated_objects_size_in_bytes));
+                      allocated_objects_size_in_bytes);
+  obj_dump->AddScalar("locked_size",
+                      base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                      locked_objects_size_in_bytes);
 
   // Emit an ownership edge towards a global allocator dump node. This allows
   // to avoid double-counting segments when both browser and child process emit