Add an intrinsified early out path for Dart timeline calls

runtime/vm/intrinsifier_mips.cc

Index: runtime/vm/intrinsifier_mips.cc
diff --git a/runtime/vm/intrinsifier_mips.cc b/runtime/vm/intrinsifier_mips.cc
index 2398a7b957d512cc3a278c788e4733e2fa33f164..5266d52693917092992a74c365cac15d582e8be8 100644
--- a/runtime/vm/intrinsifier_mips.cc
+++ b/runtime/vm/intrinsifier_mips.cc
@@ -14,6 +14,7 @@
 #include "vm/object_store.h"
 #include "vm/regexp_assembler.h"
 #include "vm/symbols.h"
+#include "vm/timeline.h"
 
 namespace dart {
 
@@ -2208,6 +2209,23 @@ void Intrinsifier::Profiler_getCurrentTag(Assembler* assembler) {
   __ delay_slot()->lw(V0, Address(V0, Isolate::current_tag_offset()));
 }
 
+
+void Intrinsifier::Timeline_isDartStreamEnabled(Assembler* assembler) {
+  Label true_label;
+  // Load TimelineStream*.
+  __ lw(V0, Address(THR, Thread::dart_stream_offset()));
+  // Load uintptr_t from TimelineStream*.
+  __ lw(V0, Address(V0, TimelineStream::enabled_offset()));
+  __ bne(V0, ZR, &true_label);
+  // Not enabled.
+  __ LoadObject(V0, Bool::False());
+  __ Ret();
+  // Enabled.
+  __ Bind(&true_label);
+  __ LoadObject(V0, Bool::True());
+  __ Ret();
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS