Reduce memory peaks when generating data urls for images.

Source/platform/graphics/ImageBuffer.cpp

Index: Source/platform/graphics/ImageBuffer.cpp
diff --git a/Source/platform/graphics/ImageBuffer.cpp b/Source/platform/graphics/ImageBuffer.cpp
index 4ea1880db0cb0eac0d88abebf9010ad21787cf92..259f8f5ab6237d3bbdee00097831abf910cfe8d7 100644
--- a/Source/platform/graphics/ImageBuffer.cpp
+++ b/Source/platform/graphics/ImageBuffer.cpp
@@ -413,6 +413,12 @@ static bool encodeImage(T& source, const String& mimeType, const double* quality
     return true;
 }
 
+static String EncodedImageToDataURL(const Vector<char>& encodedImage, const String& mimeType)
+{
+    String base64Data = base64Encode(encodedImage);
+    return "data:" + mimeType + ";base64," + base64Data;
+}
+
 String ImageBuffer::toDataURL(const String& mimeType, const double* quality) const
 {
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
@@ -420,10 +426,7 @@ String ImageBuffer::toDataURL(const String& mimeType, const double* quality) con
     Vector<char> encodedImage;
     if (!isSurfaceValid() || !encodeImage(m_surface->bitmap(), mimeType, quality, &encodedImage))
         return "data:,";
-    Vector<char> base64Data;
-    base64Encode(encodedImage, base64Data);
-
-    return "data:" + mimeType + ";base64," + base64Data;
+    return EncodedImageToDataURL(encodedImage, mimeType);

[Noel Gordon, 2014/09/11 01:03:23]

/curious would writing this as

   return "data:" + mimeType + ";base64," + base64Encode(encodedImage);

do what you want here (interpolate a Sting)?

[Daniel Bratell, 2014/09/11 11:22:31]

It would work the same. I put it in a separate method because it's done in two
different methods, and despite being a 1-2 liner it is actually a fair bit of
generated code (string constructions, destructions, copies, lots of
StringAppend<> objects and it is unnecessary to have that more than once.

 }
 
 String ImageDataToDataURL(const ImageDataBuffer& imageData, const String& mimeType, const double* quality)
@@ -433,11 +436,7 @@ String ImageDataToDataURL(const ImageDataBuffer& imageData, const String& mimeTy
     Vector<char> encodedImage;
     if (!encodeImage(imageData, mimeType, quality, &encodedImage))
         return "data:,";
-
-    Vector<char> base64Data;
-    base64Encode(encodedImage, base64Data);
-
-    return "data:" + mimeType + ";base64," + base64Data;
+    return EncodedImageToDataURL(encodedImage, mimeType);
 }
 
 } // namespace blink