Refactor creation of SadTabView into a tab helper object

ios/chrome/browser/web/sad_tab_tab_helper_unittest.mm

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/web/sad_tab_tab_helper.h"
+
+#import "ios/web/public/test/fakes/test_web_state.h"
+#import "testing/gtest/include/gtest/gtest.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+// A TestWebState which records whether a transient content view was presented
+class SadTabTabHelperTestWebState : public web::TestWebState {
+ public:
+  void ShowTransientContentView(CRWContentView* content_view) override {

[Eugene But (OOO till 7-30), 2017/04/10 22:56:28]

Do you want to update web::TestWebState instead of adding API here?

[PL, 2017/04/11 01:35:21]

I could do that no problem, but here's why I did this: it's not possible to
update TestWebState to do the right thing here without adding some flag (as it
just calls through to a CRWebController so no state change in the WebState is
currently triggered).

I didn't see other cases of flags being added like this to the main TestWebState
so I created this subclass just for the purpose of this test rather than
complicate the superclass for everyone. I saw this pattern used in other
places such as reading_list_web_state_observer_unittest.mm. 

What do you think about keeping this here?

[Eugene But (OOO till 7-30), 2017/04/11 15:17:00]

Are you sure that web::TestWebState uses CRWWebController?
This code could be useful in other places.

[Eugene But (OOO till 7-30), 2017/04/12 01:01:31]

I think you missed this comment.

[peterlaurens, 2017/04/12 17:07:38]

I did, thanks! I understand this a bit better now - you're right that
TestWebState does *not* use CRWWebController, rather I was looking at the real
implementation.

I understand the TestWebState a little better now (at first I was mistakenly
assuming it was a subclass of the real WebStateImpl), so I can add this to the
TestWebState easily. Thanks!

+    if (content_view) {
+      didShowTransientContentView = true;
+    }
+  }
+  bool DidShowTransientContentView() { return didShowTransientContentView; }
+
+ private:
+  bool didShowTransientContentView;
+};
+
+// A configurable TabHelper delegate for testing
+@interface TabHelperTestDelegate : NSObject<TabHelperDelegate>
+@property(readwrite, assign) BOOL active;
+- (BOOL)tabHelperShouldBeActive:(NSString*)tabHelperID;
+@end
+
+@implementation TabHelperTestDelegate
+@synthesize active = _active;
+- (BOOL)tabHelperShouldBeActive:(NSString*)tabHelperID {
+  return self.active;
+}
+@end
+
+// Test that the presentation-block can be triggered without a delegate

[Eugene But (OOO till 7-30), 2017/04/10 22:56:28]

nit: s/Test/Tests

From Style Guide: "These comments should be descriptive ("Opens the file")
rather than imperative ("Open the file");"
https://engdoc.corp.google.com/eng/doc/devguide/cpp/styleguide.shtml?cl=head#...

[PL, 2017/04/11 01:35:21]

Done, thanks!

+TEST(SadTabTabHelperTest, PresentationCanBeTriggered) {
+  std::unique_ptr<SadTabTabHelperTestWebState> web_state(
+      new SadTabTabHelperTestWebState());

[Eugene But (OOO till 7-30), 2017/04/10 22:56:28]

nit: How about this?:
SadTabTabHelperTestWebState web_state;
SadTabTabHelper::CreateForWebState(&web_state, nil);

[PL, 2017/04/11 01:35:21]

Done; this is great thanks!

+  SadTabTabHelper::CreateForWebState(web_state.get(), nil);

[Eugene But (OOO till 7-30), 2017/04/10 22:56:28]

Do you want to document |nil| with comments?:

SadTabTabHelper::CreateForWebState(web_state.get(), nil /*delegate*/);

[PL, 2017/04/11 01:35:22]

Done!

+
+  // WebState should not have presented a transient content view
+  EXPECT_FALSE(web_state->DidShowTransientContentView());
+
+  // Helper should get notified of render process failure and show a content
+  // view
+  web_state->OnRenderProcessGone();
+  EXPECT_TRUE(web_state->DidShowTransientContentView());
+}
+
+// Test that the presentation-block can be suppressed by the delegate
+TEST(SadTabTabHelperTest, PresentationCanBeSuppressedByDelegate) {
+  TabHelperTestDelegate* delegate = [[TabHelperTestDelegate alloc] init];
+  std::unique_ptr<SadTabTabHelperTestWebState> web_state(
+      new SadTabTabHelperTestWebState());
+  SadTabTabHelper::CreateForWebState(web_state.get(), delegate);
+
+  // WebState should not have presented a transient content view
+  EXPECT_FALSE(web_state->DidShowTransientContentView());
+
+  // Helper should get notified of render process failure
+  // But the delegate should suppress the presentation of a content view
+  web_state->OnRenderProcessGone();
+  EXPECT_FALSE(web_state->DidShowTransientContentView());
+}
+
+// Test that the presentation-block can be allowed by the delegate
+TEST(SadTabTabHelperTest, PresentationCanBeAllowedByDelegate) {
+  TabHelperTestDelegate* delegate = [[TabHelperTestDelegate alloc] init];
+  delegate.active = YES;
+  std::unique_ptr<SadTabTabHelperTestWebState> web_state(
+      new SadTabTabHelperTestWebState());
+  SadTabTabHelper::CreateForWebState(web_state.get(), delegate);
+
+  // WebState should not have presented a transient content view
+  EXPECT_FALSE(web_state->DidShowTransientContentView());
+
+  // Helper should get notified of render process failure
+  // The delegate should allow the presentation of a content view
+  web_state->OnRenderProcessGone();
+  EXPECT_TRUE(web_state->DidShowTransientContentView());
+}