Revert of Changed scavenge GC to collect unmodified references

Revert of Changed scavenge GC to collect unmodified references (patchset #9 id:160001 of https://codereview.chromium.org/1358703003/ )

Reason for revert:
[Sheriff] Speculative revert due to crbug.com/539814

Original issue's description:
> Changed scavenge GC to collect unmodified references
>
> Added a scavenge GC pass that collects unmodified references instead of
> processing object groups.  This mode can be controlled by setting
> FLAG_scavenge_remove_unmodified_objects. By default this is turned off.
> Also, modified a test case to suit the handle the new GC pass.
>
> BUG=v8:4421
> LOG=N
>
> Committed: https://crrev.com/6254019238a853c9f3c09d615ba153043f6957c7
> Cr-Commit-Position: refs/heads/master@{#31102}

TBR=jochen@chromium.org,rmcilroy@chromium.org,mythria@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4421, chromium:539814
Committed: https://crrev.com/2e1dbae08b8fcec94068bb5eb85fae03e73e84d2
Cr-Commit-Position: refs/heads/master@{#31130}

[Michael Achenbach, 2015-10-06 16:54:28]

Created Revert of Changed scavenge GC to collect unmodified references

[Michael Achenbach, 2015-10-06 16:55:33]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-10-06 16:55:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1388133002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1388133002/1

[commit-bot: I haz the power, 2015-10-06 16:56:07]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-06 16:56:09]

Failed to apply patch for test/cctest/test-api.cc:
While running git apply --index -3 -p1;
  error: patch failed: test/cctest/test-api.cc:6549
  Falling back to three-way merge...
  Applied patch to 'test/cctest/test-api.cc' with conflicts.
  U test/cctest/test-api.cc

Patch:       test/cctest/test-api.cc
Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index
edaacdb55092370ab47e86accf2f1937812da077..ab44af7f934aae2a2dde02dcdc2f7545d5ca5d26
100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -6536,8 +6536,7 @@
     Local<Object> b(v8::Object::New(iso));
     object_a.handle.Reset(iso, a);
     object_b.handle.Reset(iso, b);
-    if (interlinked &&
-        !v8::internal::FLAG_scavenge_reclaim_unmodified_objects) {
+    if (interlinked) {
       a->Set(v8_str("x"), b);
       b->Set(v8_str("x"), a);
     }
@@ -6549,8 +6548,7 @@
     // We are relying on this creating a big flag array and reserving the space
     // up front.
     v8::Handle<Value> big_array = CompileRun("new Array(50000)");
-    if (!v8::internal::FLAG_scavenge_reclaim_unmodified_objects)
-      a->Set(v8_str("y"), big_array);
+    a->Set(v8_str("y"), big_array);
     big_heap_size = CcTest::heap()->SizeOfObjects();
   }

[Michael Achenbach, 2015-10-06 17:39:24]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-10-06 17:39:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1388133002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1388133002/1

[commit-bot: I haz the power, 2015-10-06 17:39:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-06 17:39:59]

Patchset 1 (id:??) landed as
https://crrev.com/2e1dbae08b8fcec94068bb5eb85fae03e73e84d2
Cr-Commit-Position: refs/heads/master@{#31130}