Fix Autofill hang when interacting with large forms (i.e. forms containing many fields).

chrome/renderer/autofill/form_cache.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/renderer/autofill/form_cache.h"
 
 #include "base/logging.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/renderer/autofill/form_autofill_util.h"
 #include "grit/generated_resources.h"
@@ skipping 23 matching lines @@
 using webkit::forms::FormDataPredictions;
 
 namespace {
 
 // The number of fields required by Autofill.  Ideally we could send the forms
 // to Autofill no matter how many fields are in the forms; however, finding the
 // label for each field is a costly operation and we can't spare the cycles if
 // it's not necessary.
 const size_t kRequiredAutofillFields = 3;
 
-// The maximum number of form fields we are willing to parse, due to
-// computational costs.  Several examples of forms with lots of fields that are
-// not relevant to Autofill: (1) the Netflix queue; (2) the Amazon wishlist;
-// (3) router configuration pages; and (4) other configuration pages, e.g. for
-// Google code project settings.
-const size_t kMaxParseableFields = 100;
-
 }  // namespace
 
 namespace autofill {
 
 FormCache::FormCache() {
 }
 
 FormCache::~FormCache() {
 }
 
@@ skipping 24 matching lines @@
       // Save original values of <select> elements so we can restore them
       // when |ClearFormWithNode()| is invoked.
       if (IsSelectElement(element)) {
         const WebSelectElement select_element =
             element.toConst<WebSelectElement>();
         initial_select_values_.insert(std::make_pair(select_element,
                                                      select_element.value()));
       }
     }
 
-    // To avoid overly expensive computation, we impose both a minimum and a
-    // maximum number of allowable fields.
-    if (control_elements.size() < kRequiredAutofillFields ||
-        control_elements.size() > kMaxParseableFields)
+    // To avoid overly expensive computation, we impose a minimum number of
+    // allowable fields.  The corresponding maximum number of allowable fields
+    // is imposed by WebFormElementToFormData().
+    if (control_elements.size() < kRequiredAutofillFields)
       continue;
 
     FormData form;
-    WebFormElementToFormData(form_element, WebFormControlElement(),
-                             REQUIRE_NONE, EXTRACT_VALUE, &form, NULL);
+    if (!WebFormElementToFormData(form_element, WebFormControlElement(),
+                                  REQUIRE_NONE, EXTRACT_VALUE, &form, NULL)) {
+      continue;
+    }
 
     num_fields_seen += form.fields.size();
     if (num_fields_seen > kMaxParseableFields)
       break;
 
     if (form.fields.size() >= kRequiredAutofillFields)
       forms->push_back(form);
   }
 }
 
@@ skipping 137 matching lines @@
         UTF8ToUTF16(form.experiment_id));
     if (!element->hasAttribute("placeholder"))
       element->setAttribute("placeholder", WebString(UTF8ToUTF16(placeholder)));
     element->setAttribute("title", WebString(title));
   }
 
   return true;
 }
 
 }  // namespace autofill