Remove unneeded enum forward declarations

Forward declaring of enums without specifying a type is illegal. These
forward declarations only worked because they weren't needed. They were
found by VC++'s overzealous C4471 warning.

R=raymes@chromium.org

Review-Url: https://codereview.chromium.org/2835943003
Cr-Commit-Position: refs/heads/master@{#467734}

chrome/browser/download/download_target_determiner.h

@@ -26,10 +26,6 @@
 class Profile;
 class DownloadPrefs;
 
-namespace content {
-enum DownloadDangerType;
-}
-
 // Determines the target of the download.
 //
 // Terminology:

content/browser/accessibility/browser_accessibility_win.h

@@ -25,11 +25,6 @@
 #include "third_party/isimpledom/ISimpleDOMText.h"
 #include "ui/accessibility/platform/ax_platform_node_win.h"
 
-namespace ui {
-enum TextBoundaryDirection;
-enum TextBoundaryType;
-}
-
 namespace content {
 class BrowserAccessibilityRelation;
 

content/browser/renderer_host/pepper/pepper_tcp_socket_message_filter.h

@@ -35,7 +35,6 @@
 #endif  // defined(OS_CHROMEOS)
 
 namespace net {
-enum AddressFamily;
 class DrainableIOBuffer;
 class IOBuffer;
 class SSLClientSocket;

content/renderer/media/webmediaplayer_ms.h

@@ -29,7 +29,6 @@ class WebString;
 
 namespace media {
 class MediaLog;
-enum VideoRotation;
 }
 
 namespace cc_blink {