Added a kEchoCancellation constraint to turn off the audio processing.

content/renderer/media/media_stream_constraints_util.cc

+// Copyright 2014 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 "content/renderer/media/media_stream_constraints_util.h"
+
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/utf_string_conversions.h"
+#include "third_party/WebKit/public/platform/WebMediaConstraints.h"
+#include "third_party/WebKit/public/platform/WebString.h"
+
+namespace content {
+
+bool GetConstraintValue(const blink::WebMediaConstraints& constraints,
+                        const std::string& name,
+                        bool* value) {
+  int constraint_value = 0;
+  if (!GetConstraintValue(constraints, name, &constraint_value))
+    return false;
+
+  *value = static_cast<bool>(constraint_value);

[tommi (sloooow) - chröme, 2014/04/08 10:49:30]

Are you sure this works?

The values of these constraints have previously been checked as strings with
kValueTrue and kValueFalse.  Now it looks like you're attempting to convert that
to an int and from there to a bool...

[no longer working on chromium, 2014/04/11 08:56:30]

Yes, the value is stored as blink::WebString in blink, and we need to convert it
to boolean (audio constraints) or int (video constraints). We have been doing
this for long time.

+  return true;
+}
+
+bool GetConstraintValue(const blink::WebMediaConstraints& constraints,
+                        const std::string& name,
+                        int* value) {
+  return GetManatoryConstraintValue(constraints, name, value) ||
+         GetOptionalConstraintValue(constraints, name, value);
+}
+
+bool GetManatoryConstraintValue(const blink::WebMediaConstraints& constraints,

[tommi (sloooow) - chröme, 2014/04/08 10:49:30]

GetMandatoryConstraintValue
(missing 'd')

[no longer working on chromium, 2014/04/11 08:56:30]

Done.

+                                const std::string& name,
+                                int* value) {
+  blink::WebString value_str;
+  if (!constraints.getMandatoryConstraintValue(base::UTF8ToUTF16(name),
+                                               value_str))
+    return false;
+
+  base::StringToInt(value_str.utf8(), value);

[tommi (sloooow) - chröme, 2014/04/08 10:49:30]

return base::StringToInt(value_str.utf8(), value);

so that if the value isn't an int, we will report an error.

[no longer working on chromium, 2014/04/11 08:56:30]

Done.

+  return true;
+}
+
+bool GetOptionalConstraintValue(const blink::WebMediaConstraints& constraints,
+                                const std::string& name,
+                                int* value) {
+  blink::WebString value_str;
+  if (!constraints.getOptionalConstraintValue(base::UTF8ToUTF16(name),
+                                              value_str))

[tommi (sloooow) - chröme, 2014/04/08 10:49:30]

{}

[no longer working on chromium, 2014/04/11 08:56:30]

Done.

+    return false;
+
+  base::StringToInt(value_str.utf8(), value);

[tommi (sloooow) - chröme, 2014/04/08 10:49:30]

return base::StringToInt(value_str.utf8(), value);

so that if the value isn't an int, we will report an error.

[no longer working on chromium, 2014/04/11 08:56:30]

Done.

+  return true;
+}
+
+}  // namespace content