Fixes document type detection on iOS 9.

On iOS 9, evaluating '' + document always results in [object
HTMLDocument], even for PDFs. This introduces another way of checking
document type on iOS 9. Unfortunately, it doesn't work on iOS 8, so the
old implementation needs to stay too.

BUG=549604

Review URL: https://codereview.chromium.org/1458703004

Cr-Commit-Position: refs/heads/master@{#361095}
(cherry picked from commit 704def3)

Review URL: https://codereview.chromium.org/1491043004 .

Cr-Commit-Position: refs/branch-heads/2564@{#201}
Cr-Branched-From: 1283eca-refs/heads/master@{#359700}

ios/web/web_state/ui/crw_ui_web_view_web_controller.mm

@@ -4,6 +4,7 @@
 
 #import "ios/web/web_state/ui/crw_ui_web_view_web_controller.h"
 
+#import "base/ios/ios_util.h"
 #import "base/ios/ns_error_util.h"
 #import "base/ios/weak_nsobject.h"
 #include "base/json/json_reader.h"
@@ -550,13 +551,25 @@ - (BOOL)isCurrentNavigationItemPOST {
   if (!_uiWebView) {
     return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
   }
-  NSString* documentType =
-      [_uiWebView stringByEvaluatingJavaScriptFromString:
-          @"'' + document"];
-  if ([documentType isEqualToString:@"[object HTMLDocument]"])
-    return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
-  else if ([documentType isEqualToString:@"[object Document]"])
-    return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
+
+  if (base::ios::IsRunningOnIOS9OrLater()) {
+    // On iOS 9, evaluating '' + document always results in [object
+    // HTMLDocument], even for PDFs. However, document.contentType is properly
+    // defined.
+    NSString* MIMEType = [_uiWebView
+        stringByEvaluatingJavaScriptFromString:@"document.contentType"];
+    return [self documentTypeFromMIMEType:MIMEType];
+  } else {
+    // On iOS 8 and below, document.contentType is always undefined. Use this
+    // instead.
+    NSString* documentType =
+        [_uiWebView stringByEvaluatingJavaScriptFromString:@"'' + document"];
+    if ([documentType isEqualToString:@"[object HTMLDocument]"])
+      return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
+    else if ([documentType isEqualToString:@"[object Document]"])
+      return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
+  }
+
   return web::WEB_VIEW_DOCUMENT_TYPE_UNKNOWN;
 }
 

ios/web/web_state/ui/crw_web_controller+protected.h

@@ -410,6 +410,9 @@ struct NewWindowInfo {
 // Resets pending external request information.
 - (void)resetExternalRequest;
 
+// Converts MIME type string to WebViewDocumentType.
+- (web::WebViewDocumentType)documentTypeFromMIMEType:(NSString*)MIMEType;
+
 @end
 
 #endif  // IOS_WEB_WEB_STATE_UI_CRW_WEB_CONTROLLER_PROTECTED_H_

ios/web/web_state/ui/crw_web_controller.mm

@@ -3854,4 +3854,18 @@ - (void)resetExternalRequest {
   _externalRequest.reset();
 }
 
+- (web::WebViewDocumentType)documentTypeFromMIMEType:(NSString*)MIMEType {
+  if (!MIMEType.length) {
+    return web::WEB_VIEW_DOCUMENT_TYPE_UNKNOWN;
+  }
+
+  if ([MIMEType isEqualToString:@"text/html"] ||
+      [MIMEType isEqualToString:@"application/xhtml+xml"] ||
+      [MIMEType isEqualToString:@"application/xml"]) {
+    return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
+  }
+
+  return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
+}
+
 @end

ios/web/web_state/ui/crw_wk_web_view_web_controller.mm

@@ -536,17 +536,8 @@ - (BOOL)isCurrentNavigationItemPOST {
     return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
   }
 
-  std::string mimeType = self.webState->GetContentsMimeType();
-  if (mimeType.empty()) {
-    return web::WEB_VIEW_DOCUMENT_TYPE_UNKNOWN;
-  }
-
-  if (mimeType == "text/html" || mimeType == "application/xhtml+xml" ||
-      mimeType == "application/xml") {
-    return web::WEB_VIEW_DOCUMENT_TYPE_HTML;
-  }
-
-  return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
+  std::string MIMEType = self.webState->GetContentsMimeType();
+  return [self documentTypeFromMIMEType:base::SysUTF8ToNSString(MIMEType)];
 }
 
 - (void)loadRequest:(NSMutableURLRequest*)request {