[iOS] Prevent PDF Generation of Non-HTML Web States.

WKWebView was returning a blank PDF when requesting a PDF to get
generated for a loaded PDF (during full page screenshot scenario).

Fix: Disable PDF generation on non-HTML Web states.

Bug: 1131566
Change-Id: Ia5ac045b8ec1335266e98ef8cf7eb00a8c62f0d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2431553
Commit-Queue: Sebastien Lalancette <seblalancette@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810814}

ios/web/web_state/ui/crw_web_controller.mm

@@ -877,7 +877,8 @@ typedef void (^ViewportStateCompletion)(const web::PageViewportState*);
   // Invoke the |completionBlock| with nil rather than a blank PDF for certain
   // URLs.
   const GURL& URL = self.webState->GetLastCommittedURL();
-  if (!URL.is_valid() || web::GetWebClient()->IsAppSpecificURL(URL)) {
+  if (![self contentIsHTML] || !URL.is_valid() ||
+      web::GetWebClient()->IsAppSpecificURL(URL)) {
     dispatch_async(dispatch_get_main_queue(), ^{
       completionBlock(nil);
     });

ios/web/web_state/web_state_unittest.mm

@@ -299,6 +299,51 @@ TEST_F(WebStateTest, CreateFullPagePdf_InvalidURLs) {
   }
 }
 
+// Tests that CreateFullPagePdf invokes completion callback nil when the
+// WebState content is not HTML (e.g. a PDF file).
+TEST_F(WebStateTest, CreateFullPagePdfWebStatePdfContent) {
+  CGRect fake_bounds = CGRectMake(0, 0, 100, 100);
+  UIGraphicsPDFRenderer* pdf_renderer =
+      [[UIGraphicsPDFRenderer alloc] initWithBounds:fake_bounds];
+  NSData* pdf_data = [pdf_renderer
+      PDFDataWithActions:^(UIGraphicsPDFRendererContext* context) {
+        [context beginPage];
+        [[UIColor blueColor] setFill];
+        [context fillRect:fake_bounds];
+      }];
+
+  GURL test_url("https://www.chromium.org/somePDF.pdf");
+  NavigationManager::WebLoadParams load_params(test_url);
+  web_state()->GetNavigationManager()->LoadURLWithParams(load_params);
+  ASSERT_TRUE(base::test::ios::WaitUntilConditionOrTimeout(
+      base::test::ios::kWaitForPageLoadTimeout, ^bool {
+        return web_state()->GetLastCommittedURL() == test_url &&
+               !web_state()->IsLoading();
+      }));
+
+  std::string mime_type = "application/pdf";
+  web_state()->LoadData(
+      pdf_data, [NSString stringWithUTF8String:mime_type.c_str()], test_url);
+
+  ASSERT_TRUE(base::test::ios::WaitUntilConditionOrTimeout(
+      base::test::ios::kWaitForPageLoadTimeout, ^bool {
+        return !web_state()->IsLoading();
+      }));
+
+  __block NSData* callback_data = nil;
+  __block bool callback_called = false;
+  web_state()->CreateFullPagePdf(base::BindOnce(^(NSData* pdf_document_data) {
+    callback_data = [pdf_document_data copy];
+    callback_called = true;
+  }));
+
+  ASSERT_TRUE(WaitUntilConditionOrTimeout(kWaitForPageLoadTimeout, ^bool {
+    return callback_called;
+  }));
+
+  ASSERT_FALSE(callback_data);
+}
+
 // Tests that message sent from main frame triggers the ScriptCommandCallback
 // with |is_main_frame| = true.
 TEST_F(WebStateTest, MessageFromMainFrame) {