Support conversion of clamped double values for pixel arrays in Crankshaft.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 719c8d3d99e0c7f7a250ad904e3f3c1624dcad89..f377ca4c34d14c8edc8f1429a4d775006ec20ba1 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -765,6 +765,13 @@ class MacroAssembler: public Assembler {
   // jcc instructions (je, ja, jae, jb, jbe, je, and jz).
   void FCmp();
 
+  void ClampUint8(Register reg);
+
+  void ClampDoubleToUint8(XMMRegister input_reg,
+                          XMMRegister temp_xmm_reg,
+                          Register result_reg,
+                          Register temp_reg);
+
   // Abort execution if argument is not a number. Used in debug code.
   void AbortIfNotNumber(Register object);