Make the arm port build cleanly with Clang.

src/arm/macro-assembler-arm.h

Index: src/arm/macro-assembler-arm.h
diff --git a/src/arm/macro-assembler-arm.h b/src/arm/macro-assembler-arm.h
index 70659ae39a070151db646f569e28e9a50f456e4f..5722b799c23779364089d6742e2e12fa46cf03c3 100644
--- a/src/arm/macro-assembler-arm.h
+++ b/src/arm/macro-assembler-arm.h
@@ -1407,7 +1407,6 @@ class CodePatcher {
 
  private:
   byte* address_;  // The address of the code being patched.
-  int instructions_;  // Number of instructions of the expected patch size.
   int size_;  // Number of bytes of the expected patch size.
   MacroAssembler masm_;  // Macro assembler used to generate the code.
 };