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 <sstream>
+
+#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 {
+
+namespace {
+
+// Convert a string ("true", "false") to a boolean.
+bool ConvertStringToBoolean(const std::string& string, bool* value) {
+  std::istringstream iss(string);
+  iss >> std::boolalpha >> *value;
+  return !iss.fail();
+}
+
+}  // namespace
+
+bool GetConstraintValueAsBoolean(const blink::WebMediaConstraints& constraints,
+                                 const std::string& key,
+                                 bool* value) {
+  return GetMandatoryConstraintValueAsBoolean(constraints, key, value) ||
+         GetOptionalConstraintValueAsBoolean(constraints, key, value);
+}
+
+bool GetConstraintValueAsInteger(const blink::WebMediaConstraints& constraints,

[tommi (sloooow) - chröme, 2014/05/03 10:26:28]

Thanks for changing these.  It was still stuck in my head when you used these
functions in earlier patch sets to convert string->int->bool.

[no longer working on chromium, 2014/05/05 12:55:57]

NP.

+                                 const std::string& key,
+                                 int* value) {
+  return GetMandatoryConstraintValueAsInteger(constraints, key, value) ||
+         GetOptionalConstraintValueAsInteger(constraints, key, value);
+}
+
+bool GetConstraintValueAsString(const blink::WebMediaConstraints& constraints,
+                                const std::string& key,
+                                std::string* value) {
+  blink::WebString value_str;
+  if (!constraints.getMandatoryConstraintValue(base::UTF8ToUTF16(key),

[tommi (sloooow) - chröme, 2014/05/03 10:26:28]

nit: Do the base::UTF8ToUTF16 conversion only once

[no longer working on chromium, 2014/05/05 12:55:57]

Done.

+                                               value_str) &&
+      !constraints.getOptionalConstraintValue(base::UTF8ToUTF16(key),
+                                              value_str)) {
+    return false;
+  }
+
+  *value = value_str.utf8();
+  return true;
+}
+
+bool GetMandatoryConstraintValueAsBoolean(
+    const blink::WebMediaConstraints& constraints,
+    const std::string& key,
+    bool* value) {
+  blink::WebString value_str;
+  if (!constraints.getMandatoryConstraintValue(base::UTF8ToUTF16(key),
+                                               value_str)) {
+    return false;
+  }
+
+  return ConvertStringToBoolean(value_str.utf8(), value);
+}
+
+bool GetMandatoryConstraintValueAsInteger(
+    const blink::WebMediaConstraints& constraints,
+    const std::string& key,
+    int* value) {
+  blink::WebString value_str;
+  if (!constraints.getMandatoryConstraintValue(base::UTF8ToUTF16(key),
+                                               value_str)) {
+    return false;
+  }
+
+  return base::StringToInt(value_str.utf8(), value);
+}
+
+bool GetOptionalConstraintValueAsBoolean(
+    const blink::WebMediaConstraints& constraints,
+    const std::string& key,
+    bool* value) {
+  blink::WebString value_str;
+  if (!constraints.getOptionalConstraintValue(base::UTF8ToUTF16(key),
+                                              value_str)) {
+    return false;
+  }
+
+  return ConvertStringToBoolean(value_str.utf8(), value);
+}
+
+bool GetOptionalConstraintValueAsInteger(
+    const blink::WebMediaConstraints& constraints,
+    const std::string& key,
+    int* value) {
+  blink::WebString value_str;
+  if (!constraints.getOptionalConstraintValue(base::UTF8ToUTF16(key),
+                                              value_str)) {
+    return false;
+  }
+
+  return base::StringToInt(value_str.utf8(), value);
+}
+
+}  // namespace content