ARM64: Preserve x8 and x9 when necessary.

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index 9a8cd467a0f7b8425c6dabe754f9f7f89cc54686..a5784a6f23ca6f967d0f3537f2665b1624af0ad6 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -516,8 +516,8 @@ class CPURegList {
   void Combine(const CPURegList& other);
 
   // Remove every register in the other CPURegList from this one. Registers that
-  // do not exist in this list are ignored. The type and size of the registers
-  // in the 'other' list must match those in this list.
+  // do not exist in this list are ignored. The type of the registers in the
+  // 'other' list must match those in this list.
   void Remove(const CPURegList& other);
 
   // Variants of Combine and Remove which take CPURegisters.