Avoid to unconditionally include rtc_base/win32.h.

This CL adds #error to spot where rtc_base/win32.h is unconditionally
included and fixes all the places where it happens.

Bug: webrtc:8814
Change-Id: I3c005acf2cdb58a51f1bcaa4acaeebd272c56660
Reviewed-on: https://webrtc-review.googlesource.com/46060
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21840}

examples/peerconnection/client/main_wnd.h

@@ -20,7 +20,9 @@
 #include "examples/peerconnection/client/peer_connection_client.h"
 #include "media/base/mediachannel.h"
 #include "media/base/videocommon.h"
+#if defined(WEBRTC_WIN)
 #include "rtc_base/win32.h"
+#endif  // WEBRTC_WIN
 
 class MainWndCallback {
  public:

media/engine/webrtcvideocapturer.cc

@@ -20,7 +20,10 @@
 #include "rtc_base/timeutils.h"
 
 #include "modules/video_capture/video_capture_factory.h"
+
+#if defined(WEBRTC_WIN)
 #include "rtc_base/win32.h"  // Need this to #include the impl files.
+#endif  // WEBRTC_WIN
 #include "system_wrappers/include/field_trial.h"
 
 namespace cricket {

rtc_base/ipaddress.cc

@@ -31,7 +31,10 @@
 #include "rtc_base/logging.h"
 #include "rtc_base/nethelpers.h"
 #include "rtc_base/stringutils.h"
+
+#if defined(WEBRTC_WIN)
 #include "rtc_base/win32.h"
+#endif  // WEBRTC_WIN
 
 namespace rtc {
 

rtc_base/openssladapter.cc

@@ -14,8 +14,10 @@
 #include <unistd.h>
 #endif
 
+#if defined(WEBRTC_WIN)
 // Must be included first before openssl headers.
 #include "rtc_base/win32.h"  // NOLINT
+#endif  // WEBRTC_WIN
 
 #include <openssl/bio.h>
 #include <openssl/crypto.h>

rtc_base/opensslidentity.cc

@@ -12,8 +12,10 @@
 
 #include <memory>
 
+#if defined(WEBRTC_WIN)
 // Must be included first before openssl headers.
 #include "rtc_base/win32.h"  // NOLINT
+#endif  // WEBRTC_WIN
 
 #include <openssl/bio.h>
 #include <openssl/bn.h>

rtc_base/win32.h

@@ -11,7 +11,9 @@
 #ifndef RTC_BASE_WIN32_H_
 #define RTC_BASE_WIN32_H_
 
-#if defined(WEBRTC_WIN)
+#ifndef WEBRTC_WIN
+#error "Only #include this header in Windows builds"
+#endif
 
 #ifndef WIN32_LEAN_AND_MEAN
 #define WIN32_LEAN_AND_MEAN
@@ -83,5 +85,4 @@ inline bool IsCurrentProcessLowIntegrity() {
 
 }  // namespace rtc
 
-#endif  // WEBRTC_WIN
 #endif  // RTC_BASE_WIN32_H_