Revert "[ic] Internalize strings on the fly in KeyedLoadICGeneric."

This reverts commit 6366a010.

Reason for revert: Breaks layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/19429

Original change's description:
> [ic] Internalize strings on the fly in KeyedLoadICGeneric.
> 
> This turns on the existing --internalize_on_the_fly flag for the
> MEGAMORPHIC KeyedLoadIC to properly internalize strings before
> looking up the property. This avoids the otherwise taken runtime
> call to %KeyedGetProperty, which is definitely slower.
> 
> Initially the --internalize_on_the_fly flag was turned off because
> internalizing strings on the fly causes too much traffic on the
> megamorphic stub cache. We avoid this problem here by not probing
> the stub cache in that case, which still gives the benefit of not
> having to go to the runtime.
> 
> This improves the babylon test on the web-tooling-benchmark by around
> 2-3% and will probably also help with several tests (like React or
> Ember) on the Speedometer benchmark.
> 
> If this CL causes trouble (i.e. tanks something important), we can
> just turn off the --internalize_on_the_fly flag again.
> 
> Bug: v8:6936, v8:7026
> Change-Id: Ia59a8a3799d9624d831d66b05bae3ecef31cee0a
> Reviewed-on: https://chromium-review.googlesource.com/750821
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49072}

TBR=ishell@chromium.org,bmeurer@chromium.org

Change-Id: I5345eb29016ecd6b7788b1b49b2f53992ea82b58
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6936, v8:7026
Reviewed-on: https://chromium-review.googlesource.com/750904Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49077}

src/flag-definitions.h

@@ -304,7 +304,7 @@ DEFINE_BOOL(trace_block_coverage, false,
 DEFINE_BOOL(feedback_normalization, false,
             "feed back normalization to constructors")
 // TODO(jkummerow): This currently adds too much load on the stub cache.
-DEFINE_BOOL_READONLY(internalize_on_the_fly, true,
+DEFINE_BOOL_READONLY(internalize_on_the_fly, false,
                      "internalize string keys for generic keyed ICs on the fly")
 
 // Flags for optimization types.

src/ic/accessor-assembler.cc

@@ -2400,32 +2400,14 @@ void AccessorAssembler::KeyedLoadICGeneric(const LoadICParameters* p) {
   BIND(&if_notunique);
   {
     if (FLAG_internalize_on_the_fly) {
-      Label if_in_string_table(this), if_not_in_string_table(this);
-      TryInternalizeString(p->name, &if_index, &var_index, &if_in_string_table,
-                           &var_unique, &if_not_in_string_table, &slow);
+      Label not_in_string_table(this);
+      TryInternalizeString(p->name, &if_index, &var_index, &if_unique_name,
+                           &var_unique, &not_in_string_table, &slow);
 
-      BIND(&if_in_string_table);
-      {
-        // TODO(bmeurer): We currently use a version of GenericPropertyLoad
-        // here, where we don't try to probe the megamorphic stub cache after
-        // successfully internalizing the incoming string. Past experiments
-        // with this have shown that it causes too much traffic on the stub
-        // cache. We may want to re-evaluate that in the future. Original
-        // note on the --internalize_on_the_fly flag:
-        //
-        // TODO(jkummerow): This currently adds too much load on the stub cache.
-        LoadICParameters pp = *p;
-        pp.name = var_unique.value();
-        GenericPropertyLoad(receiver, receiver_map, instance_type, &pp, &slow,
-                            kDontUseStubCache);
-      }
-
-      BIND(&if_not_in_string_table);
-      {
-        // If the string was not found in the string table, then no object can
-        // have a property with that name.
-        Return(UndefinedConstant());
-      }
+      BIND(&not_in_string_table);
+      // If the string was not found in the string table, then no object can
+      // have a property with that name.
+      Return(UndefinedConstant());
     } else {
       Goto(&slow);
     }