[New PassKit] Gracefully handle pkpass download on iPad.

On iPad PKAddPassesViewController alloc/init returns nil. This CL fixes
a crash, which caused by presenting nil view controller.

The functional behavior remains the same as for old pass kit
implementaiton (the error is silentry ignored). This issues is tracked
in a separate bug (crbug.com/794301).

Bug: 787943
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Id3826fa13d5c327795d411b3ec7b9c5d343031c1
Reviewed-on: https://chromium-review.googlesource.com/823239Reviewed-by: Gregory Chatzinoff <gchatz@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523804}

ios/chrome/browser/ui/download/pass_kit_coordinator.mm

@@ -71,6 +71,10 @@
 
 // Presents PKAddPassesViewController.
 - (void)presentAddPassUI {
+  if (![PKAddPassesViewController canAddPasses]) {
+    [self stop];
+    return;
+  }
   _viewController = [[PKAddPassesViewController alloc] initWithPass:self.pass];
   _viewController.delegate = self;
   [self.baseViewController presentViewController:_viewController

ios/chrome/browser/ui/download/pass_kit_coordinator_unittest.mm

@@ -27,6 +27,7 @@
 #endif
 
 using testing::WaitUntilConditionOrTimeout;
+using testing::kWaitForUIElementTimeout;
 
 // Test fixture for PassKitCoordinator class.
 class PassKitCoordinatorTest : public PlatformTest {
@@ -57,11 +58,6 @@ class PassKitCoordinatorTest : public PlatformTest {
 // Tests that PassKitCoordinator presents PKAddPassesViewController for the
 // valid PKPass object.
 TEST_F(PassKitCoordinatorTest, ValidPassKitObject) {
-  if (IsIPadIdiom()) {
-    // Wallet app is not supported on iPads.
-    return;
-  }
-
   std::string data = testing::GetTestPass();
   NSData* nsdata = [NSData dataWithBytes:data.c_str() length:data.size()];
   PKPass* pass = [[PKPass alloc] initWithData:nsdata error:nil];
@@ -72,16 +68,21 @@ TEST_F(PassKitCoordinatorTest, ValidPassKitObject) {
       presentDialogForPass:pass
                   webState:web_state_.get()];
 
-  EXPECT_TRUE(WaitUntilConditionOrTimeout(testing::kWaitForUIElementTimeout, ^{
+  if (IsIPadIdiom()) {
+    // Wallet app is not supported on iPads.
+  } else {
+    EXPECT_TRUE(WaitUntilConditionOrTimeout(kWaitForUIElementTimeout, ^{
       return [base_view_controller_.presentedViewController class] ==
              [PKAddPassesViewController class];
     }));
 
     [coordinator_ stop];
 
-  EXPECT_TRUE(WaitUntilConditionOrTimeout(testing::kWaitForUIElementTimeout, ^{
+    EXPECT_TRUE(WaitUntilConditionOrTimeout(kWaitForUIElementTimeout, ^{
       return base_view_controller_.presentedViewController == nil;
     }));
+  }
+
   EXPECT_FALSE(coordinator_.webState);
   EXPECT_FALSE(coordinator_.pass);
 }