[tracing] Add method to create "weak" global dumps

base/trace_event/memory_allocator_dump.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_
 #define BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/trace_event/memory_allocator_dump_guid.h"
 #include "base/values.h"
 
 namespace base {
 namespace trace_event {
 
 class MemoryDumpManager;
 class ProcessMemoryDump;
 class TracedValue;
 
 // Data model for user-land memory allocator dumps.
 class BASE_EXPORT MemoryAllocatorDump {
  public:
+  enum Flag {

[Primiano Tucci (use gerrit), 2016/01/19 17:07:11]

s/Flag/Flags/

[ssid, 2016/01/20 18:58:34]

Done.

+    // A dump marked weak will be removed from tracing. It is used when dump

[Primiano Tucci (use gerrit), 2016/01/19 17:07:11]

I'd clarify and say "will be discarded by TraceViewer" instead of "will be
removed from tracing".
I'd remove the "It is used when..." part as adds IMHO more confusion.

[ssid, 2016/01/20 18:58:34]

Done.

+    // provider is unsure of the existence of a block of memory.
+    WEAK = 1 << 0,
+  };
+
   // MemoryAllocatorDump is owned by ProcessMemoryDump.
   MemoryAllocatorDump(const std::string& absolute_name,
                       ProcessMemoryDump* process_memory_dump,
                       const MemoryAllocatorDumpGuid& guid);
   MemoryAllocatorDump(const std::string& absolute_name,
                       ProcessMemoryDump* process_memory_dump);
   ~MemoryAllocatorDump();
 
   // Standard attribute |name|s for the AddScalar and AddString() methods.
   static const char kNameSize[];          // To represent allocated space.
@@ skipping 22 matching lines @@
   const std::string& absolute_name() const { return absolute_name_; }
 
   // Called at trace generation time to populate the TracedValue.
   void AsValueInto(TracedValue* value) const;
 
   // Get the ProcessMemoryDump instance that owns this.
   ProcessMemoryDump* process_memory_dump() const {
     return process_memory_dump_;
   }
 
+  // Use enum Flag to set values.
+  void set_flags(uint8_t flags) { flags_ |= flags; }

[Primiano Tucci (use gerrit), 2016/01/19 17:07:11]

Why not just int (there seems to be lot of precedent in the codebase)? After all
is not going to really save those 24 bits :)

[ssid, 2016/01/20 18:58:34]

Done.

+  void unset_flags(uint8_t flags) { flags_ &= ~flags; }

[Primiano Tucci (use gerrit), 2016/01/19 17:07:11]

s/unset/clear/

[ssid, 2016/01/20 18:58:34]

Done.

+  uint8_t flags() { return flags_; }
+
   // |guid| is an optional global dump identifier, unique across all processes
   // within the scope of a global dump. It is only required when using the
   // graph APIs (see TODO_method_name) to express retention / suballocation or
   // cross process sharing. See crbug.com/492102 for design docs.
   // Subsequent MemoryAllocatorDump(s) with the same |absolute_name| are
   // expected to have the same guid.
   const MemoryAllocatorDumpGuid& guid() const { return guid_; }
 
   TracedValue* attributes_for_testing() const { return attributes_.get(); }
 
  private:
   const std::string absolute_name_;
   ProcessMemoryDump* const process_memory_dump_;  // Not owned (PMD owns this).
   scoped_refptr<TracedValue> attributes_;
   MemoryAllocatorDumpGuid guid_;
+  uint8_t flags_;  // See enum Flag.

[Primiano Tucci (use gerrit), 2016/01/19 17:07:11]

ditto here for int

[ssid, 2016/01/20 18:58:34]

Done.

 
   // A local buffer for Sprintf conversion on fastpath. Avoids allocating
   // temporary strings on each AddScalar() call.
   std::string string_conversion_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryAllocatorDump);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_