[crankshaft] Remove useless --optimize-for-in flag.

R=jarin@chromium.org
BUG=v8:3650
LOG=n

Review URL: https://codereview.chromium.org/1621583002

Cr-Commit-Position: refs/heads/master@{#33453}

src/bailout-reason.h

@@ -78,8 +78,6 @@ namespace internal {
   V(kExportDeclaration, "Export declaration")                                  \
   V(kExternalStringExpectedButNotFound,                                        \
     "External string expected, but not found")                                 \
-  V(kForInStatementOptimizationIsDisabled,                                     \
-    "ForInStatement optimization is disabled")                                 \
   V(kForInStatementWithNonLocalEachVariable,                                   \
     "ForInStatement with non-local each variable")                             \
   V(kForOfStatement, "ForOfStatement")                                         \

src/crankshaft/hydrogen.cc

@@ -5290,10 +5290,6 @@ void HOptimizedGraphBuilder::VisitForInStatement(ForInStatement* stmt) {
   DCHECK(current_block() != NULL);
   DCHECK(current_block()->HasPredecessor());
 
-  if (!FLAG_optimize_for_in) {
-    return Bailout(kForInStatementOptimizationIsDisabled);
-  }
-
   if (!stmt->each()->IsVariableProxy() ||
       !stmt->each()->AsVariableProxy()->var()->IsStackLocal()) {
     return Bailout(kForInStatementWithNonLocalEachVariable);

src/flag-definitions.h

@@ -393,8 +393,6 @@ DEFINE_BOOL(inline_accessors, true, "inline JavaScript accessors")
 DEFINE_INT(escape_analysis_iterations, 2,
            "maximum number of escape analysis fix-point iterations")
 
-DEFINE_BOOL(optimize_for_in, true, "optimize functions containing for-in loops")
-
 DEFINE_BOOL(concurrent_recompilation, true,
             "optimizing hot functions asynchronously on a separate thread")
 DEFINE_BOOL(trace_concurrent_recompilation, false,

test/mjsunit/compiler/optimized-for-in.js

@@ -25,8 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --optimize-for-in --allow-natives-syntax
-// Flags: --no-concurrent-osr
+// Flags: --allow-natives-syntax --no-concurrent-osr
 
 // Test for-in support in Crankshaft.  For simplicity this tests assumes certain
 // fixed iteration order for properties and will have to be adjusted if V8