Add Tracing.requestMemoryDump method to DevTools API (tracing handler)

base/trace_event/memory_dump_manager.cc

Index: base/trace_event/memory_dump_manager.cc
diff --git a/base/trace_event/memory_dump_manager.cc b/base/trace_event/memory_dump_manager.cc
index ea2760b118fb4043238df92416b14c7326523f72..24f520a1d1f7b620052a98460700280215b136f3 100644
--- a/base/trace_event/memory_dump_manager.cc
+++ b/base/trace_event/memory_dump_manager.cc
@@ -276,7 +276,9 @@ void MemoryDumpManager::ContinueAsyncProcessDump(
       skip_dump = true;
     } else if (mdp == g_mmaps_dump_provider &&
                pmd_async_state->req_args.dump_type !=
-                   MemoryDumpType::PERIODIC_INTERVAL_WITH_MMAPS) {
+                   MemoryDumpType::PERIODIC_INTERVAL_WITH_MMAPS &&
+               pmd_async_state->req_args.dump_type !=
+                   MemoryDumpType::EXPLICITLY_TRIGGERED) {
       // Mmaps dumping is very heavyweight and cannot be performed at the same
       // rate of other dumps. TODO(primiano): this is a hack and should be
       // cleaned up as part of crbug.com/499731.