Backlog of Qt and QtWebKit problems

Qt problems

• ARM optimized qdrawhelper is only enabled for RCVT (symbian) . The needs to be transferred to gcc inline assembly. This will optimize memfill, Source, SourceOver and some blend functions.

• ARMv6 should be auto detected. Currently arm/armv6 can be passed as -embedded options. The benefit of ARMv6 in src/corelib is the use of atomic load and exchange, instead of the old "swap" extension. __ARCH_ARM_6__ should be used to detect it.

• Enabled pld (preload) in qdrawhelper for ARMv5te and upwards

• QImageReader deserves some optimatations. E.g. decode to the QImage provided to the decoder, do not parse every gif when trying to determine the size.

• Changes to QHttpNetworkReply to reduce memory reallocations. Reserve some bytes instead of doing QByteArray::append all them time.

• Cut down on the usage of QUrl::toEncoded as it shows up in the profile of starting jobs.

QtWebKit problems

• Image decoder changes to greatly reduce memory and load speed. See this ​bug for planned changes. The possible impact is quite big. The task would be to change the ImageDecoderQt to perform better and create the benchmark to compare WebCore decoders with Qt ones to assist with future optimations in QImageReader.

• Loading of ​http://en.wikipedia.org/wiki/Maxwell_equations is triggering bad "scheduling". The loading_standalone test has been extracted but is not able to highlight the problem. This is a Qt and QtWebKit issue, it must be understood first.

• TCmalloc needs to be tested. Does it make anything faster/slower? How to test memory fragmentation.

• The fuzz testing will make QtWebKit go in infinite loops and stop working. This situation needs to be analyzed as this can be a serve reliabality problem.