Turn off SupportsFlexibleFloorAndRound for Arm64 due to a bug.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 8219f3ed2200af69a9e1bae3e97c179300f60b4f..73c0d013575f28553ed17918769986131a58cec1 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -2574,7 +2574,9 @@ class HUnaryMathOperation FINAL : public HTemplateInstruction<2> {
   // Math.round.
   bool SupportsFlexibleFloorAndRound() const {
 #ifdef V8_TARGET_ARCH_ARM64
-    return true;
+    // TODO(rmcilroy): Re-enable this for Arm64 once http://crbug.com/476477 is
+    // fixed.
+    return false;
 #else
     return false;
 #endif