[tracing] Sanitize process memory dumps for background mode

base/trace_event/process_memory_dump.h

Index: base/trace_event/process_memory_dump.h
diff --git a/base/trace_event/process_memory_dump.h b/base/trace_event/process_memory_dump.h
index c18e10c374459182d6fae2cafa22aa5ae80ae9d9..f6d7090dd175c44fba4dd4d5c584ade80ecfb27e 100644
--- a/base/trace_event/process_memory_dump.h
+++ b/base/trace_event/process_memory_dump.h
@@ -34,6 +34,13 @@ class MemoryDumpManager;
 class MemoryDumpSessionState;
 class TracedValue;
 
+// Args for ProcessMemoryDump. Dump providers are expected to read the args for
+// creating dumps.
+struct MemoryDumpArgs {
+  // Specifies how detailed the dumps should be.
+  MemoryDumpLevelOfDetail level_of_detail;
+};
+
 // ProcessMemoryDump is as a strongly typed container which holds the dumps
 // produced by the MemoryDumpProvider(s) for a specific process.
 class BASE_EXPORT ProcessMemoryDump {
@@ -67,7 +74,8 @@ class BASE_EXPORT ProcessMemoryDump {
   static size_t CountResidentBytes(void* start_address, size_t mapped_size);
 #endif
 
-  ProcessMemoryDump(scoped_refptr<MemoryDumpSessionState> session_state);
+  ProcessMemoryDump(scoped_refptr<MemoryDumpSessionState> session_state,
+                    const MemoryDumpArgs& dump_args);
   ~ProcessMemoryDump();
 
   // Creates a new MemoryAllocatorDump with the given name and returns the
@@ -175,7 +183,16 @@ class BASE_EXPORT ProcessMemoryDump {
 
   const HeapDumpsMap& heap_dumps() const { return heap_dumps_; }
 
+  const MemoryDumpArgs& dump_args() const { return dump_args_; }
+
+  MemoryAllocatorDump* black_hole_mad_for_testing() {
+    return black_hole_mad_.get();
+  }
+
  private:
+  friend class ProcessMemoryDumpTest;
+  FRIEND_TEST_ALL_PREFIXES(ProcessMemoryDumpTest, BackgroundModeTest);
+
   MemoryAllocatorDump* AddAllocatorDumpInternal(
       std::unique_ptr<MemoryAllocatorDump> mad);
 
@@ -194,6 +211,14 @@ class BASE_EXPORT ProcessMemoryDump {
   // Keeps track of relationships between MemoryAllocatorDump(s).
   std::vector<MemoryAllocatorDumpEdge> allocator_dumps_edges_;
 
+  // Level of detail of the current dump.
+  const MemoryDumpArgs dump_args_;
+
+  // This allocator dump is returned when an invalid dump is created in
+  // background mode. The attributes of the dump are ignored and not added to
+  // the trace.
+  std::unique_ptr<MemoryAllocatorDump> black_hole_mad_;
+
   DISALLOW_COPY_AND_ASSIGN(ProcessMemoryDump);
 };