Avoid uninitialized member warning on gcc 4.3.4

Patch by Bert Belder.

Review URL: http://codereview.chromium.org/7553011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8791 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/lithium-codegen-ia32.cc

@@ -1459,7 +1459,7 @@ void LCodeGen::DoBranch(LBranch* instr) {
         DeoptimizeIf(zero, instr->environment());
       }
 
-      Register map;
+      Register map = no_reg;
       if (expected.NeedsMap()) {
         map = ToRegister(instr->TempAt(0));
         ASSERT(!map.is(reg));