ARM64: Update code after the VIXL 1.6 release.

We now leave the assembler buffer management to VIXL.

Change-Id: Ieefe83cf5cf5e1ab8c924b0e7dc03af6a55053ae
diff --git a/compiler/utils/arm64/assembler_arm64.h b/compiler/utils/arm64/assembler_arm64.h
index bf89d24..373fd34 100644
--- a/compiler/utils/arm64/assembler_arm64.h
+++ b/compiler/utils/arm64/assembler_arm64.h
@@ -59,12 +59,12 @@
 
 class Arm64Assembler FINAL : public Assembler {
  public:
-  Arm64Assembler() : vixl_buf_(new byte[kBufferSizeArm64]),
-  vixl_masm_(new vixl::MacroAssembler(vixl_buf_, kBufferSizeArm64)) {}
+  // We indicate the size of the initial code generation buffer to the VIXL
+  // assembler. From there we it will automatically manage the buffer.
+  Arm64Assembler() : vixl_masm_(new vixl::MacroAssembler(kArm64BaseBufferSize)) {}
 
   virtual ~Arm64Assembler() {
     delete vixl_masm_;
-    delete[] vixl_buf_;
   }
 
   // Emit slow paths queued during assembly.
@@ -213,9 +213,6 @@
   void AddConstant(Register rd, int32_t value, vixl::Condition cond = vixl::al);
   void AddConstant(Register rd, Register rn, int32_t value, vixl::Condition cond = vixl::al);
 
-  // Vixl buffer.
-  byte* vixl_buf_;
-
   // Vixl assembler.
   vixl::MacroAssembler* vixl_masm_;