Remove workaround for GVR crash when backing out of DON flow.

The GVR crash has been fixed, so we can remove our workaround (which
was to wait 10 seconds before allowing re-entry into VR)

The workaround was added in
https://chromium-review.googlesource.com/c/chromium/src/+/624294

Bug: 759575
Change-Id: Iad46c0575d15c1eb7d67d46253eea50294243ae8
Reviewed-on: https://chromium-review.googlesource.com/776620
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Yash Malik <ymalik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517464}

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java

@@ -107,7 +107,6 @@ public class VrShellDelegate
 
     private static final long REENTER_VR_TIMEOUT_MS = 1000;
     private static final int EXPECT_DON_TIMEOUT_MS = 2000;
-    private static final long ENTER_VR_FAILED_TIMEOUT_MS = 10000;
 
     private static final String FEEDBACK_REPORT_TYPE = "USER_INITIATED_FEEDBACK_REPORT_VR";
 
@@ -175,8 +174,6 @@ public class VrShellDelegate
     // presentation experience.
     private boolean mVrBrowserUsed;
 
-    private boolean mWaitingForVrTimeout;
-
     private boolean mDensityChanged;
 
     // Gets run when the user exits VR mode by clicking the 'x' button or system UI back button.
@@ -1086,7 +1083,6 @@ public class VrShellDelegate
     private int enterVrInternal() {
         if (mPaused) return ENTER_VR_CANCELLED;
         if (mInVr) return ENTER_VR_NOT_NECESSARY;
-        if (mWaitingForVrTimeout) return ENTER_VR_CANCELLED;
 
         // Update VR support level as it can change at runtime
         maybeUpdateVrSupportLevel();
@@ -1197,13 +1193,6 @@ public class VrShellDelegate
             maybeSetPresentResult(false, mDonSucceeded);
 
             shutdownVr(true, false);
-            mWaitingForVrTimeout = true;
-            new Handler().postDelayed(new Runnable() {
-                @Override
-                public void run() {
-                    mWaitingForVrTimeout = false;
-                }
-            }, ENTER_VR_FAILED_TIMEOUT_MS);
         }
 
         mProbablyInDon = false;