Delete ArtMethod gc_map_ field

Moved the gc_map field from OatMethod to OatQuickMethodHeader.
Deleted the ArtMethod gc_map_ field.

Bug: 17643507

Change-Id: Ifa0470c3e4c2f8a319744464d94c6838b76b3d48

(cherry picked from commit 807140048f82a2b87ee5bcf337f23b6a3d1d5269)
diff --git a/compiler/oat_test.cc b/compiler/oat_test.cc
index ce4ed6d..9fe98e3 100644
--- a/compiler/oat_test.cc
+++ b/compiler/oat_test.cc
@@ -190,8 +190,8 @@
   // If this test is failing and you have to update these constants,
   // it is time to update OatHeader::kOatVersion
   EXPECT_EQ(84U, sizeof(OatHeader));
-  EXPECT_EQ(8U, sizeof(OatMethodOffsets));
-  EXPECT_EQ(24U, sizeof(OatQuickMethodHeader));
+  EXPECT_EQ(4U, sizeof(OatMethodOffsets));
+  EXPECT_EQ(28U, sizeof(OatQuickMethodHeader));
   EXPECT_EQ(91 * GetInstructionSetPointerSize(kRuntimeISA), sizeof(QuickEntryPoints));
 }