Added AVFoundation Glue and Device Monitoring for Mac.

media/video/capture/mac/avfoundation_glue.mm

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "media/video/capture/mac/avfoundation_glue.h"
+
+#include <dlfcn.h>
+
+#include "base/mac/mac_util.h"
+
+BOOL AVFoundationGlue::IsAVFoundationSupported() {
+  return (base::mac::IsOSLionOrLater() && [AVFoundationBundle() load]);
+}
+
+NSBundle const* AVFoundationGlue::AVFoundationBundle() {
+  static NSBundle* bundle = [NSBundle
+      bundleWithPath:@"/System/Library/Frameworks/AVFoundation.framework"];
+  return bundle;
+}
+
+void* AVFoundationGlue::AVFoundationLibraryHandle() {
+  const char* library_path =
+      [[AVFoundationBundle() executablePath] fileSystemRepresentation];
+  if (library_path == NULL) {
+    DCHECK(false);
+    return NULL;
+  }
+  static void* library_handle = dlopen(library_path, RTLD_LAZY | RTLD_LOCAL);

[DaleCurtis, 2013/10/22 19:17:56]

Presumably rsesek@ and mmentovai@ decided against using base::NativeLibrary ?

[mcasas, 2013/10/23 12:52:08]

base::NativeLibrary uses CFBundle and we are using here NSBundle, for a reason
lost in the threads, perhaps mmentovai@ or rsesek@ can comment on that?

+  DCHECK(library_handle) << dlerror();
+  return library_handle;
+}
+
+NSString* AVFoundationGlue::AVCaptureDeviceWasConnectedNotification() {
+  return ReadNSStringPtr("AVCaptureDeviceWasConnectedNotification");
+}
+
+NSString* AVFoundationGlue::AVCaptureDeviceWasDisconnectedNotification() {
+  return ReadNSStringPtr("AVCaptureDeviceWasDisconnectedNotification");
+}
+
+NSString* AVFoundationGlue::AVMediaTypeVideo() {
+  return ReadNSStringPtr("AVMediaTypeVideo");
+}
+
+NSString* AVFoundationGlue::AVMediaTypeAudio() {
+  return ReadNSStringPtr("AVMediaTypeAudio");
+}
+
+NSString* AVFoundationGlue::AVMediaTypeMuxed() {
+  return ReadNSStringPtr("AVMediaTypeMuxed");
+}
+
+NSString* AVFoundationGlue::ReadNSStringPtr(char const* const symbol) {

[DaleCurtis, 2013/10/22 19:17:56]

"const char* symbol" is normally how this is written.  What's the weird notation
buying you?

[mcasas, 2013/10/23 12:52:08]

"const char* symbol" would be a mutable-pointer pointing to a constant-contents
char array. Here I wanted to say constant-pointer pointing to a
constant-contents char array. 

The extra constant-ness does not justify the readiness so I changed it back to
"const char*".

+  NSString** stringPointer = reinterpret_cast<NSString**>(

[DaleCurtis, 2013/10/22 19:17:56]

string_pointer ?

[mcasas, 2013/10/23 12:52:08]

Absolutely. Done.

+      dlsym(AVFoundationLibraryHandle(), symbol));
+  DCHECK(stringPointer) << dlerror();
+  return *stringPointer;
+}
+
+@implementation AVCaptureDeviceGlue
+
++ (NSArray*)devices {
+  Class avcClass =
+      [AVFoundationGlue::AVFoundationBundle() classNamed:@"AVCaptureDevice"];
+  SEL selectorDevices = NSSelectorFromString(@"devices");
+  if ([avcClass respondsToSelector:selectorDevices]) {
+    return [avcClass performSelector:selectorDevices];
+  }
+  return nil;
+}
+
++ (BOOL)hasMediaType:(NSString*)mediaType
+    forCaptureDevice:(CrAVCaptureDevice*)device {
+  SEL selectorHasMediaType = NSSelectorFromString(@"hasMediaType:");
+  if ([device respondsToSelector:selectorHasMediaType]) {
+    return [device hasMediaType:mediaType];
+  }
+  return NO;
+}
+
++ (NSString*)uniqueID:(CrAVCaptureDevice*)device {
+  SEL selectorUniqueID = NSSelectorFromString(@"uniqueID");
+  if ([device respondsToSelector:selectorUniqueID]) {
+    return [device uniqueID];
+  }
+  return nil;
+}
+
+@end  // @implementation AVCaptureDevice