[Payment Handler] canMakePayment() is true for JIT install.

Before this patch, if the only method of payment available was a payment
handler that is not yet installed, but is available or installation
Just-In-Time (JIT), then PaymentRequest.canMakePayment() would return
"false". This prevented JIT installable payment handler usage by
merchants that don't call PaymentRequest.show() unless
PaymentRequest.canMakePayment() returns true.

This patch makes canMakePayment() return "true" for JIT installable
payment handlers on both desktop and Android. (iOS does not support
payment handlers at this point.)

After this patch, if the only method of payment available is a payment
handler that is not yet installed, but is available for JIT
installation, then PaymentRequest.canMakePayment() would return "true".

Bug: 877644
Change-Id: I614a02789b514d5d0e7738ca827178a844e74199
Reviewed-on: https://chromium-review.googlesource.com/1188900
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Reviewed-by: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586252}

chrome/android/java/src/org/chromium/chrome/browser/payments/ServiceWorkerPaymentApp.java

@@ -355,12 +355,6 @@ public class ServiceWorkerPaymentApp extends PaymentInstrument implements Paymen
     @Override
     public void dismissInstrument() {}
 
-    @Override
-    public boolean canMakePayment() {
-        // Return false for PaymentRequest.canMakePayment() if installation is needed.
-        return !mNeedsInstallation;
-    }
-
     @Override
     public boolean canPreselect() {
         return mCanPreselect;

components/payments/content/service_worker_payment_instrument.cc

@@ -279,15 +279,9 @@ base::string16 ServiceWorkerPaymentInstrument::GetMissingInfoLabel() const {
 }
 
 bool ServiceWorkerPaymentInstrument::IsValidForCanMakePayment() const {
-  // This instrument should not be used when can_make_payment_result_ is false
-  // , so this interface should not be invoked.
+  // This instrument should not be used when can_make_payment_result_ is false,
+  // so this interface should not be invoked.
   DCHECK(can_make_payment_result_);
-
-  // Returns false for PaymentRequest.CanMakePayment query if the app needs
-  // installation.
-  if (needs_installation_)
-    return false;
-
   return true;
 }