Dispatch separate MIDIMessageEvents for multiple messages in the received data buffer.

Source/modules/webmidi/MIDIInput.cpp

Index: Source/modules/webmidi/MIDIInput.cpp
diff --git a/Source/modules/webmidi/MIDIInput.cpp b/Source/modules/webmidi/MIDIInput.cpp
index a5dee099588ff1cf228b26c9234b4e538f9e97da..1e9e62c80095d7bcfaa742d97850f4bb4e8f32a0 100644
--- a/Source/modules/webmidi/MIDIInput.cpp
+++ b/Source/modules/webmidi/MIDIInput.cpp
@@ -49,10 +49,30 @@ void MIDIInput::didReceiveMIDIData(unsigned portIndex, const unsigned char* data
 {
     ASSERT(isMainThread());
 
-    RefPtr<Uint8Array> array = Uint8Array::create(length);
-    array->setRange(data, length, 0);
+    // The received MIDI data may contain one or more messages.
+    // The Web MIDI API requires that a separate event be dispatched for each message,
+    // so we walk through the data and dispatch one at a time.
+    size_t i = 0;
+    while (i < length) {
+        unsigned char status = data[i];
+        unsigned char strippedStatus = status & 0xf0;
 
-    dispatchEvent(MIDIMessageEvent::create(timeStamp, array));
+        // FIXME: support System Exclusive.
+        if (strippedStatus >= 0xf0)
+            break;
+
+        // All non System Exclusive messages have a total size of 3 except for Program Change and Channel Pressure.
+        size_t totalMessageSize = (strippedStatus == 0xc0 || strippedStatus == 0xd0) ? 2 : 3;
+
+        if (i + totalMessageSize <= length) {
+            RefPtr<Uint8Array> array = Uint8Array::create(totalMessageSize);
+            array->setRange(data + i, totalMessageSize, 0);
+
+            dispatchEvent(MIDIMessageEvent::create(timeStamp, array));
+        }
+
+        i += totalMessageSize;
+    }
 }
 
 } // namespace WebCore