Implement ImageData constructors.

Source/core/html/ImageData.cpp

Index: Source/core/html/ImageData.cpp
diff --git a/Source/core/html/ImageData.cpp b/Source/core/html/ImageData.cpp
index bcba908180f35739d9b4140b77e6a1d7968b8a86..bf11b580a6ffa6856582b849bf465a66436f1ed9 100644
--- a/Source/core/html/ImageData.cpp
+++ b/Source/core/html/ImageData.cpp
@@ -29,6 +29,9 @@
 #include "config.h"
 #include "core/html/ImageData.h"
 
+#include "bindings/v8/ExceptionState.h"
+#include "core/dom/ExceptionCode.h"
+
 namespace WebCore {
 
 PassRefPtr<ImageData> ImageData::create(const IntSize& size)
@@ -57,6 +60,57 @@ PassRefPtr<ImageData> ImageData::create(const IntSize& size, PassRefPtr<Uint8Cla
     return adoptRef(new ImageData(size, byteArray));
 }
 
+PassRefPtr<ImageData> ImageData::create(unsigned width, unsigned height, ExceptionState& exceptionState)
+{
+    if (!width || !height) {
+        exceptionState.throwDOMException(IndexSizeError, String::format("The source %s is zero or non-finite.", width ? "height" : "width"));

[Justin Novosad, 2014/03/19 19:35:54]

how can an unsigned be non-finite?

[sof, 2014/03/19 19:41:10]

ToUInt32() maps Inf and NaNs (including non-numbers mapped to such by
ToNumber()) to 0. "not a number" is a better term to use here.

+        return nullptr;
+    }
+
+    Checked<unsigned, RecordOverflow> dataSize = 4;
+    dataSize *= width;
+    dataSize *= height;
+    if (dataSize.hasOverflowed()) {
+        exceptionState.throwDOMException(IndexSizeError, "The requested image size exceeds the supported range.");
+        return nullptr;
+    }
+
+    RefPtr<ImageData> imageData = adoptRef(new ImageData(IntSize(width, height)));
+    imageData->data()->zeroFill();
+    return imageData;

[Inactive, 2014/03/19 19:07:14]

nit: .release()

+}
+
+PassRefPtr<ImageData> ImageData::create(Uint8ClampedArray* data, unsigned width, unsigned height, ExceptionState& exceptionState)
+{
+    if (!data) {
+        exceptionState.throwTypeError("Expected a Uint8ClampedArray as first argument.");
+        return nullptr;
+    }
+    if (!width) {
+        exceptionState.throwDOMException(IndexSizeError, "The source width is zero or non-finite.");
+        return nullptr;
+    }
+
+    Uint8ClampedArray* clampedData = static_cast<Uint8ClampedArray*>(data);

[Inactive, 2014/03/19 19:07:14]

Why is this cast needed?

I actually don't understand by we need this local variable at all. We should be
able to use "data" directly unless I am missing something.

[sof, 2014/03/19 22:19:16]

Yes, doesn't make much sense; gone. [I belatedly discovered that the IDL
compiler supported Uint8ClampedArray instance checking, and not just
ArrayBufferViews; this is a remnant.]

+    unsigned clampedLength = clampedData->length() / 4;

[Justin Novosad, 2014/03/19 19:35:54]

According to the spec you need to throw an InvalidStateError if
clampedData->length() is not a multiple of 4. You should perform that check
before this division.

[sof, 2014/03/19 22:19:16]

Thanks, quite right. Addressed + expanded the testing in this area.

+    if (!clampedLength) {
+        exceptionState.throwDOMException(IndexSizeError, "The input data has a zero byte length.");
+        return nullptr;
+    }
+    if (clampedLength % width) {
+        exceptionState.throwDOMException(IndexSizeError, "The byte length of the input data is not a multiple of (4 * width).");
+        return nullptr;
+    }
+    if (!height) {
+        height = clampedLength / width;
+    } else if (height != clampedLength / width) {
+        exceptionState.throwDOMException(IndexSizeError, "The byte length of the input data is not equal to (4 * width * height).");
+        return nullptr;
+    }
+
+    return adoptRef(new ImageData(IntSize(width, height), clampedData));
+}
+
 ImageData::ImageData(const IntSize& size)
     : m_size(size)
     , m_data(Uint8ClampedArray::createUninitialized(size.width() * size.height() * 4))