Android: Remove ContentViewCore::GetLayer() from public interface

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java
index 549522b06076f7a527584683603bbe73ff11f7f0..a6591a00affdb19dc4f5f5ef595e2dbb32f4fef1 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java
@@ -21,6 +21,7 @@ import org.chromium.chrome.browser.NativePage;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.tabmodel.TabModelUtils;
+import org.chromium.content_public.browser.WebContents;
 import org.chromium.ui.base.DeviceFormFactor;
 
 import java.io.File;
@@ -234,7 +235,8 @@ public class TabContentManager {
                         mThumbnailScale);
                 nativePageBitmap.recycle();
             } else {
-                nativeCacheTab(mNativeTabContentManager, tab, tab.getContentViewCore(),
+                if (tab.getWebContents() == null) return;
+                nativeCacheTab(mNativeTabContentManager, tab, tab.getWebContents(),
                         mThumbnailScale);
             }
         }
@@ -361,7 +363,7 @@ public class TabContentManager {
             int compressionQueueMaxSize, int writeQueueMaxSize, boolean useApproximationThumbnail);
     private native boolean nativeHasFullCachedThumbnail(long nativeTabContentManager, int tabId);
     private native void nativeCacheTab(long nativeTabContentManager, Object tab,
-            Object contentViewCore, float thumbnailScale);
+            WebContents webContents, float thumbnailScale);
     private native void nativeCacheTabWithBitmap(long nativeTabContentManager, Object tab,
             Object bitmap, float thumbnailScale);
     private native void nativeInvalidateIfChanged(long nativeTabContentManager, int tabId,