Revert "weblayer: fixs enum conversions"

This reverts commit 0b9effbc.

Reason for revert: looks like this broke try bots, see https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8897429937364092048/+/steps/compile__with_patch_/0/stdout 

Original change's description:
> weblayer: fixs enum conversions
> 
> These got lost in the rename.
> 
> BUG=none
> TEST=none
> 
> Change-Id: Ifea2d13329f4a2c739657d918ae93c929ede5499
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1902708
> Auto-Submit: Scott Violet <sky@chromium.org>
> Reviewed-by: John Abd-El-Malek <jam@chromium.org>
> Commit-Queue: Scott Violet <sky@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#713455}

TBR=sky@chromium.org,jam@chromium.org

Change-Id: Ib68648d7601f6d940dc6a8d509ac32535940fcb2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: none
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1904327Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713475}

weblayer/browser/java/org/chromium/weblayer_private/NewTabCallbackProxy.java

@@ -9,7 +9,6 @@ import android.os.RemoteException;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.annotations.NativeMethods;
-import org.chromium.weblayer_private.interfaces.NewTabType;
 
 /**
  * Owns the c++ NewTabCallback class, which is responsible for forwarding all
@@ -31,24 +30,8 @@ public final class NewTabCallbackProxy {
         mNativeNewTabCallbackProxy = 0;
     }
 
-    @NewTabType
-    private static int implTypeToJavaType(@ImplNewTabType int type) {
-        switch (type) {
-            case ImplNewTabType.FOREGROUND_TAB:
-                return NewTabType.FOREGROUND_TAB;
-            case ImplNewTabType.BACKGROUND_TAB:
-                return NewTabType.BACKGROUND_TAB;
-            case ImplNewTabType.NEW_POPUP:
-                return NewTabType.NEW_POPUP;
-            case ImplNewTabType.NEW_WINDOW:
-                return NewTabType.NEW_WINDOW;
-        }
-        assert false;
-        return NewTabType.FOREGROUND_TAB;
-    }
-
     @CalledByNative
-    public void onNewTab(long nativeTab, @ImplNewTabType int mode) throws RemoteException {
+    public void onNewTab(long nativeTab, int mode) throws RemoteException {
         // This class should only be created while the tab is attached to a fragment.
         assert mTab.getBrowser() != null;
         TabImpl tab =