Add more informative messages for DOM exceptions.

Source/modules/webaudio/AudioNode.cpp

Index: Source/modules/webaudio/AudioNode.cpp
diff --git a/Source/modules/webaudio/AudioNode.cpp b/Source/modules/webaudio/AudioNode.cpp
index 0e66fd12f366797aac7a1b8de3ae1f9cfc7fffc1..cfa38af15b3d32dd9d2d3d6a72ee5a0b37c5979f 100644
--- a/Source/modules/webaudio/AudioNode.cpp
+++ b/Source/modules/webaudio/AudioNode.cpp
@@ -28,6 +28,7 @@
 
 #include "modules/webaudio/AudioNode.h"
 
+#include "bindings/v8/ExceptionMessages.h"
 #include "bindings/v8/ExceptionState.h"
 #include "core/dom/ExceptionCode.h"
 #include "modules/webaudio/AudioContext.h"
@@ -130,23 +131,43 @@ void AudioNode::connect(AudioNode* destination, unsigned outputIndex, unsigned i
     AudioContext::AutoLocker locker(context());
 
     if (!destination) {
-        es.throwUninformativeAndGenericDOMException(SyntaxError);
+        es.throwDOMException(
+            SyntaxError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "invalid destination node."));
         return;
     }
 
     // Sanity check input and output indices.
     if (outputIndex >= numberOfOutputs()) {
-        es.throwUninformativeAndGenericDOMException(IndexSizeError);
+        es.throwDOMException(
+            IndexSizeError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "invalid output index."));

[Mike West, 2013/09/27 06:44:39]

"The provided output index (8) is larger than the number of outputs (3)."

         return;
     }
 
     if (destination && inputIndex >= destination->numberOfInputs()) {
-        es.throwUninformativeAndGenericDOMException(IndexSizeError);
+        es.throwDOMException(
+            IndexSizeError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "invalid input index."));

[Mike West, 2013/09/27 06:44:39]

Same as above.

         return;
     }
 
     if (context() != destination->context()) {
-        es.throwUninformativeAndGenericDOMException(SyntaxError);
+        es.throwDOMException(
+            SyntaxError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "invalid destination context."));
         return;
     }
 
@@ -164,17 +185,32 @@ void AudioNode::connect(AudioParam* param, unsigned outputIndex, ExceptionState&
     AudioContext::AutoLocker locker(context());
 
     if (!param) {
-        es.throwUninformativeAndGenericDOMException(SyntaxError);
+        es.throwDOMException(
+            SyntaxError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "invalid AudioParam."));
         return;
     }
 
     if (outputIndex >= numberOfOutputs()) {
-        es.throwUninformativeAndGenericDOMException(IndexSizeError);
+        es.throwDOMException(
+            IndexSizeError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "invalid output index."));
         return;
     }
 
     if (context() != param->context()) {
-        es.throwUninformativeAndGenericDOMException(SyntaxError);
+        es.throwDOMException(
+            SyntaxError,
+            ExceptionMessages::failedToExecute(
+                "connect",
+                "AudioNode",
+                "destination context is different."));
         return;
     }
 
@@ -189,7 +225,12 @@ void AudioNode::disconnect(unsigned outputIndex, ExceptionState& es)
 
     // Sanity check input and output indices.
     if (outputIndex >= numberOfOutputs()) {
-        es.throwUninformativeAndGenericDOMException(IndexSizeError);
+        es.throwDOMException(
+            IndexSizeError,
+            ExceptionMessages::failedToExecute(
+                "disconnect",
+                "AudioNode",
+                "invalid output index."));

[Mike West, 2013/09/27 06:44:39]

Same as above.

         return;
     }
 
@@ -214,7 +255,12 @@ void AudioNode::setChannelCount(unsigned long channelCount, ExceptionState& es)
                 updateChannelsForInputs();
         }
     } else {
-        es.throwUninformativeAndGenericDOMException(InvalidStateError);
+        es.throwDOMException(
+            InvalidStateError,
+            ExceptionMessages::failedToSet(
+                "channelCount",
+                "AudioNode",
+                "invalid number of channels."));

[Mike West, 2013/09/27 06:44:39]

Perhaps split this into "The channel count may not be 0." and "The provided
channel count (x) is greater than the maximum number of channels supported (y)."

     }
 }
 
@@ -239,14 +285,20 @@ void AudioNode::setChannelCountMode(const String& mode, ExceptionState& es)
 
     ChannelCountMode oldMode = m_channelCountMode;
 
-    if (mode == "max")
+    if (mode == "max") {
         m_channelCountMode = Max;
-    else if (mode == "clamped-max")
+    } else if (mode == "clamped-max") {
         m_channelCountMode = ClampedMax;
-    else if (mode == "explicit")
+    } else if (mode == "explicit") {
         m_channelCountMode = Explicit;
-    else
-        es.throwUninformativeAndGenericDOMException(InvalidStateError);
+    } else {
+        es.throwDOMException(
+            InvalidStateError,
+            ExceptionMessages::failedToSet(
+                "channelCountMode",
+                "AudioNode",
+                "must be \"max\", \"clamped-max\", or \"explicit\"."));

[Mike West, 2013/09/27 06:44:39]

I'd suggest including the developer's input here: "The provided mode '" + mode +
"' is invalid. Only 'x', 'y', and 'z' are supported."

I've also generally been using single-quotes to denote code in error messages,
but that's pure preference without any real rationale behind it.

[Raymond Toy (Google), 2013/09/27 16:24:10]

Agreed.
I originally had single quotes, but kind of wanted to distinguish how you print
messages vs the values.  Currently we print something like

Failed to set `channelCountMode' of `AudioNode': must be "max", "clamped-max",
"explicit".

Not sure if this distinction is necessary. Single quotes are fine with me.

+    }
 
     if (m_channelCountMode != oldMode)
         updateChannelsForInputs();
@@ -269,12 +321,18 @@ void AudioNode::setChannelInterpretation(const String& interpretation, Exception
     ASSERT(isMainThread());
     AudioContext::AutoLocker locker(context());
 
-    if (interpretation == "speakers")
+    if (interpretation == "speakers") {
         m_channelInterpretation = AudioBus::Speakers;
-    else if (interpretation == "discrete")
+    } else if (interpretation == "discrete") {
         m_channelInterpretation = AudioBus::Discrete;
-    else
-        es.throwUninformativeAndGenericDOMException(InvalidStateError);
+    } else {
+        es.throwDOMException(
+            InvalidStateError,
+            ExceptionMessages::failedToSet(
+                "channelInterpretation",
+                "AudioNode",
+                "must be \"speakers\" or \"discrete\"."));

[Mike West, 2013/09/27 06:44:39]

Same as above.

+    }
 }
 
 void AudioNode::updateChannelsForInputs()