[Web Payments] Use OriginalProfile for IdentityProvider in PR

This CL fixes a crash in Incognito where the Payment Request
IdentityProvider attempted to register an Observer on a null
SigninManager. It also brings Payment Request in line with Autofill,
where previously PR was displaying the Original Profile's Autofill data
but wasn't able to unlock cards because the IdentityProvider was invalid
in Incognito.

Bug: 813275
Change-Id: I3fb43ba45404f8884a300d77fda7f8fe0f8364af
Reviewed-on: https://chromium-review.googlesource.com/926563
Commit-Queue: anthonyvd <anthonyvd@chromium.org>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537826}

chrome/browser/ui/views/payments/cvc_unmask_view_controller.cc

@@ -61,7 +61,8 @@ CvcUnmaskViewController::CvcUnmaskViewController(
           Profile::FromBrowserContext(web_contents_->GetBrowserContext())
               ->GetPrefs(),
           IdentityManagerFactory::GetInstance()->GetForProfile(
-              Profile::FromBrowserContext(web_contents_->GetBrowserContext())),
+              Profile::FromBrowserContext(web_contents_->GetBrowserContext())
+                  ->GetOriginalProfile()),
           /*unmask_delegate=*/this,
           /*save_delegate=*/nullptr),
       full_card_request_(this,