Fix test-hashing after recent changes to string hashing.

src/arm/macro-assembler-arm.h

Index: src/arm/macro-assembler-arm.h
===================================================================
--- src/arm/macro-assembler-arm.h	(revision 10343)
+++ src/arm/macro-assembler-arm.h	(working copy)
@@ -52,7 +52,7 @@
 
 // Give alias names to registers
 const Register cp = { 8 };  // JavaScript context pointer
-const Register roots = { 10 };  // Roots array pointer.
+const Register kRootRegister = { 10 };  // Roots array pointer.
 
 // Flags used for the AllocateInNewSpace functions.
 enum AllocationFlags {
@@ -499,6 +499,12 @@
                                     Register map,
                                     Register scratch);
 
+  void InitializeRootRegister() {
+    ExternalReference roots_array_start =
+        ExternalReference::roots_array_start(isolate());
+    mov(kRootRegister, Operand(roots_array_start));
+  }
+
   // ---------------------------------------------------------------------------
   // JavaScript invokes