[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/content/renderer/form_autofill_util.cc

Index: components/autofill/content/renderer/form_autofill_util.cc
diff --git a/components/autofill/content/renderer/form_autofill_util.cc b/components/autofill/content/renderer/form_autofill_util.cc
index c9ebc62c3996f80d2205c16dd60be43d3a05382f..2babe0c6682dbc604d5f8c41b36156d0c7e31069 100644
--- a/components/autofill/content/renderer/form_autofill_util.cc
+++ b/components/autofill/content/renderer/form_autofill_util.cc
@@ -16,6 +16,7 @@
 #include "components/autofill/core/common/autofill_data_validation.h"
 #include "components/autofill/core/common/autofill_regexes.h"
 #include "components/autofill/core/common/autofill_switches.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/autofill/core/common/form_data.h"
 #include "components/autofill/core/common/form_field_data.h"
 #include "third_party/WebKit/public/platform/WebString.h"
@@ -871,9 +872,14 @@ void PreviewFormField(const FormFieldData& data,
   if (is_initiating_node &&
       (IsTextInput(input_element) || IsTextAreaElement(*field))) {
     // Select the part of the text that the user didn't type.
-    int start = field->value().length();
-    int end = field->suggestedValue().length();
-    field->setSelectionRange(start, end);
+    if (IsFeatureSubstringMatchEnabled()) {
+      size_t start = autofill::GetTextSelectionStart(field->suggestedValue(),

[please use gerrit instead, 2015/06/11 19:10:26]

As in previous comment, recalculating the |start| seems like a bad design. The
code here uses field->suggestedValue() to set the selected range. I think that
WebFormControlElement should also contain suggestedValueStart() accessor and
setSuggestedValueStart(int) setter. (Blink uses ints for range offsets by
convention.) This is one of the files that you will need to modify in Blink:

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

Unfortunately Blink is still a separate repository, so you would need to create
a separate patch. I can guide you through creating it, but you will need an LG
from a Blink owner, who may have their own requirements. (One important thing to
take care of will be a clear comment explaining the purpose of
suggestedValueStart().) Once your Blink change lands, the code here will become
much simpler.

filed->setSelectionRange(field->suggestedValueStart(),
                         field->suggetedValue().length());

[Pritam Nikam, 2015/06/12 11:09:11]

As mentioned in my previous comment, blink side modifications will be needed if
we calculate & cache |start| indices on browser-process side along the
suggestions and pass these over IPC to the renderer for text range selection to
preview fields/forms.

IPC calls involve:
1. Autocomplete: AutofillMsg_PreviewFieldWithValue
2. Autofill form & CC name: AutofillMsg_PreviewForm
3. Password forms: AutofillMsg_PreviewPasswordSuggestion

Please correct my understanding.

[please use gerrit instead, 2015/06/22 00:32:59]

Looks right.
This IPC does not send the actual element over the wire. It's using the member
variable |element_|. So no need to modify this particular method.
Looks right.
Your understanding is correct.

[Pritam Nikam, 2015/06/22 18:31:39]

Acknowledged.

+                                                     field->value());
+      field->setSelectionRange(start, field->suggestedValue().length());
+    } else {
+      field->setSelectionRange(field->value().length(),
+                               field->suggestedValue().length());
+    }
   }
 }