Bug 683514 - Use GL_EXT_unpack_subimage when available (part 2). r=joe

The previous patch used the extension in GLContext::TexImage2D, but not
TexSubImage2D. This patch corrects that and makes sure to use the extension
in both cases.

gfx/thebes/GLContext.cpp

@@ -1854,9 +1854,9 @@ GLContext::TexImage2D(GLenum target, GLint level, GLint internalformat,
     if (rowLength > mMaxTextureSize)
       useUnpackRowLength = false;
 
-    if (useUnpackRowLength)
+    if (useUnpackRowLength) {
         fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, rowLength);
-    else if (stride != width * pixelsize) {
+    } else if (stride != width * pixelsize) {
         // Not using the whole row of texture data and GLES doesn't 
         // support GL_UNPACK_ROW_LENGTH. We need to upload each row
         // separately.
@@ -1916,9 +1916,18 @@ GLContext::TexSubImage2D(GLenum target, GLint level,
                         GetAddressAlignment((ptrdiff_t)stride)));
 
 #ifndef USE_GLES2
-    fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, stride/pixelsize);
+    bool useUnpackRowLength = true;
 #else
-    if (stride != width * pixelsize) {
+    bool useUnpackRowLength = IsExtensionSupported(EXT_unpack_subimage);
+#endif
+
+    int rowLength = stride/pixelsize;
+    if (rowLength > mMaxTextureSize)
+      useUnpackRowLength = false;
+
+    if (useUnpackRowLength) {
+        fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, rowLength);
+    } else if (stride != width * pixelsize) {
         // Not using the whole row of texture data and GLES doesn't 
         // support GL_UNPACK_ROW_LENGTH. We need to upload each row
         // separately.
@@ -1940,7 +1949,6 @@ GLContext::TexSubImage2D(GLenum target, GLint level,
         fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
         return;
     }
-#endif
 
     fTexSubImage2D(target,
                    level,
@@ -1952,9 +1960,8 @@ GLContext::TexSubImage2D(GLenum target, GLint level,
                    type,
                    pixels);
 
-#ifndef USE_GLES2
-    fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);
-#endif
+    if (useUnpackRowLength)
+        fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);
     fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
 }