diff --git a/webrtc/base/criticalsection.h b/webrtc/base/criticalsection.h
index c78e818f93..088e72e142 100644
--- a/webrtc/base/criticalsection.h
+++ b/webrtc/base/criticalsection.h
@@ -27,30 +27,8 @@
 #include <pthread.h>
 #endif
 
-#if defined(WEBRTC_MAC)
-// TODO(tommi): This is a temporary test to see if critical section objects are
-// somehow causing pointer co-member variables that follow a critical section
-// variable, are somehow throwing off the alignment and causing crash on
-// the Mac 10.9 debug bot:
-// http://build.chromium.org/p/chromium.mac/builders/Mac10.9%20Tests%20(dbg)
-#define _MUTEX_ALIGNMENT __attribute__((__aligned__(8)))
-#define _STATIC_ASSERT_CRITICAL_SECTION_SIZE() \
-    static_assert(sizeof(CriticalSection) % 8 == 0, \
-                "Bad size of CriticalSection")
-
-#else
-#define _MUTEX_ALIGNMENT
-#define _STATIC_ASSERT_CRITICAL_SECTION_SIZE()
-#endif
-
 #ifdef _DEBUG
-#if defined(WEBRTC_MAC)
-// TODO(tommi): This is related to the comment above. It looks like the
-// pthread_t member might be throwing off the mac debug bots (10.9).
-#define CS_TRACK_OWNER 0
-#else
 #define CS_TRACK_OWNER 1
-#endif
 #endif  // _DEBUG
 
 #if CS_TRACK_OWNER
@@ -90,7 +68,6 @@ class LOCKABLE CriticalSection {
 class LOCKABLE CriticalSection {
  public:
   CriticalSection() {
-    _STATIC_ASSERT_CRITICAL_SECTION_SIZE();
     pthread_mutexattr_t mutex_attribute;
     pthread_mutexattr_init(&mutex_attribute);
     pthread_mutexattr_settype(&mutex_attribute, PTHREAD_MUTEX_RECURSIVE);
@@ -127,7 +104,7 @@ class LOCKABLE CriticalSection {
   }
 
  private:
-  _MUTEX_ALIGNMENT pthread_mutex_t mutex_;
+  pthread_mutex_t mutex_;
   TRACK_OWNER(pthread_t thread_);
 };
 #endif // WEBRTC_POSIX
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 05e1ba3ec2..9fec935bc8 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -178,6 +178,26 @@
       ['rtc_relative_path==1', {
         'defines': ['EXPAT_RELATIVE_PATH',],
       }],
+      ['os_posix==1', {
+        'configurations': {
+          'Debug_Base': {
+            'defines': [
+              # Chromium's build/common.gypi defines _DEBUG for all posix
+              # _except_ for ios & mac.  The size of data types such as
+              # pthread_mutex_t varies between release and debug builds
+              # and is controlled via this flag.  Since we now share code
+              # between base/base.gyp and build/common.gypi (this file),
+              # both gyp(i) files, must consistently set this flag uniformly
+              # or else we'll run in to hard-to-figure-out problems where
+              # one compilation unit uses code from another but expects
+              # differently laid out types.
+              # For WebRTC, we want it there as well, because ASSERT and
+              # friends trigger off of it.
+              '_DEBUG',
+            ],
+          },
+        },
+      }],
       ['build_with_chromium==1', {
         'defines': [
           # Changes settings for Chromium build.
@@ -202,16 +222,6 @@
         ],
         'conditions': [
           ['os_posix==1', {
-            'configurations': {
-              'Debug_Base': {
-                'defines': [
-                  # Chromium's build/common.gypi defines this for all posix
-                  # _except_ for ios & mac.  We want it there as well, e.g.
-                  # because ASSERT and friends trigger off of it.
-                  '_DEBUG',
-                ],
-              },
-            },
             'conditions': [
               # -Wextra is currently disabled in Chromium's common.gypi. Enable
               # for targets that can handle it. For Android/arm64 right now