Remove tcmalloc when not being used. Restore shim on Windows.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index f67961a1ecc65f0f4af284a24e8f460095658533..0f049fba34527e8dfe89efe81ed55f8ba520884b 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -1258,7 +1258,7 @@
     #  'win_use_allocator_shim': 0,
     #  'win_release_RuntimeLibrary': 2
     # to ~/.gyp/include.gypi, gclient runhooks --force, and do a release build.
-    'win_use_allocator_shim%': 0, # 1 = shim allocator via libcmt; 0 = msvcrt
+    'win_use_allocator_shim%': 1, # 1 = shim allocator via libcmt; 0 = msvcrt
 
     # TODO(bradnelson): eliminate this when possible.
     # To allow local gyp files to prevent release.vsprops from being included.
@@ -2768,10 +2768,11 @@
       ['tracing_like_official_build!=0', {
         'defines': ['TRACING_IS_OFFICIAL_BUILD=1'],
       }],  # tracing_like_official_build!=0
-      ['win_use_allocator_shim==0', {
+      ['OS=="win"', {
+        'defines': ['NO_TCMALLOC'],
         'conditions': [
-          ['OS=="win"', {
-            'defines': ['NO_TCMALLOC'],
+          ['win_use_allocator_shim==1', {
+            'defines': ['ALLOCATOR_SHIM'],
           }],
         ],
       }],
@@ -3429,7 +3430,7 @@
               'WTF_USE_DYNAMIC_ANNOTATIONS=1',
             ],
           }],
-          ['OS=="win" and win_use_allocator_shim==0', {
+          ['OS=="win"', {
             'defines': ['NO_TCMALLOC'],
           }],
           # _FORTIFY_SOURCE isn't really supported by Clang now, see