Set a non-null profile in TMSPS even if IncognitoTabModel returns null.

|IncognitoTabModelImpl#getProfile| returns null, and that makes
|TabModelSelectorProfileSupplier| provides null profile to the callers.
Null profile causes crashes on |IdentityDiscController| that uses
TMSPS to observe profile changes. This CL sets a non-null profile in
TMSPS, even if IncognitoTabModelImpl returns null profile.

Bug: 1124597, 1124653
Change-Id: I48c248865294cf5415333e9653d2f7773a9910b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391154Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Patrick Noland <pnoland@chromium.org>
Commit-Queue: Side YILMAZ <sideyilmaz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806438}

chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabModelSelectorProfileSupplier.java

@@ -57,7 +57,15 @@ public class TabModelSelectorProfileSupplier
 
     @Override
     public void onTabStateInitialized() {
-        set(mSelector.getCurrentModel().getProfile());
+        Profile profile = mSelector.getCurrentModel().getProfile();
+        if (profile == null) {
+            // Since only IncognitoTabModelImpl provides null profile, the current model should be
+            // off-the-record.
+            assert mSelector.getCurrentModel().isIncognito();
+            // TODO(https://crbug.com/1060940): Update to cover all OTR profiles.
+            profile = Profile.getLastUsedRegularProfile().getPrimaryOTRProfile();
+        }
+        set(profile);
     }
 
     public void destroy() {