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

components/autofill/content/renderer/autofill_agent.cc

Index: components/autofill/content/renderer/autofill_agent.cc
diff --git a/components/autofill/content/renderer/autofill_agent.cc b/components/autofill/content/renderer/autofill_agent.cc
index 79542aff2520a500debcf60c29699d73e28d5524..c072040e475f059d94564214675392a2b7b97467 100644
--- a/components/autofill/content/renderer/autofill_agent.cc
+++ b/components/autofill/content/renderer/autofill_agent.cc
@@ -22,6 +22,7 @@
 #include "components/autofill/core/common/autofill_constants.h"
 #include "components/autofill/core/common/autofill_data_validation.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_data_predictions.h"
 #include "components/autofill/core/common/form_field_data.h"
@@ -740,8 +741,14 @@ void AutofillAgent::PreviewFieldWithValue(const base::string16& value,
   was_query_node_autofilled_ = element_.isAutofilled();
   node->setSuggestedValue(value.substr(0, node->maxLength()));
   node->setAutofilled(true);
-  node->setSelectionRange(node->value().length(),
-                          node->suggestedValue().length());
+
+  if (IsFeatureSubstringMatchEnabled()) {

[please use gerrit instead, 2015/06/28 00:43:03]

You can inline this:

node->setSelectionRange(
    IsFeatureSubstringMatchEnabled()
        ? autofill::GetTextSelectionStart(value, node->value())
        : node->value().length(),
    node->suggestedValue().length());

You use this code in at least two places. It's a good candidate to be placed
into autofill_util.h. Please do that. You can call it PreviewSuggestion() or
something better you can come up with.

[Pritam Nikam, 2015/06/29 15:38:21]

Sure, I'll move this code restructuring under |PreviewSuggestion()| API.
However, moving it to |autofill_util.h| will be a problem, as
|PreviewSuggestion()| will have blink dependency i.e. class WebInputElement, and
it'll not fly. Instead I've moved it to |form_autofill_util.h| i.e. under
content/renderer folder.

[please use gerrit instead, 2015/06/29 17:06:45]

Sounds good.

+    size_t start = autofill::GetTextSelectionStart(value, node->value());
+    node->setSelectionRange(start, node->suggestedValue().length());
+  } else {
+    node->setSelectionRange(node->value().length(),
+                            node->suggestedValue().length());
+  }
 }
 
 void AutofillAgent::ProcessForms() {