Add chrome.memoryBenchmarking.requestMemoryDump() API

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 04b6e3aa33fc15a868cd18c9696e05a1ad1fe15c..2d3d48d4216a738ac66daf25e18cc7dcc7498f41 100644
--- a/base/trace_event/memory_dump_manager.cc
+++ b/base/trace_event/memory_dump_manager.cc
@@ -272,7 +272,9 @@ 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.