Performance/load performance implement

Implement is in 'xmloff', and each element processing is divided into several steps:

       1 )processElement() : Process element
               2) _startElement() : Start element
               3) processSubContexts() : Sub elements process, 
                                 if this element is a parent element.
                                 Every sub element processing will be divided into three steps.
                       4)_createChildContext(): Create Sub Context 
                       5)_processSubContext(): Process sub element 
                       7)_collectSubContext(): Collect the sub element's result data 
               9) _characters(): Process element's content
               10)_endElement(): End element

       11)commit(): commit the result data to parent element

And every parent element has three solutions to process sub elements:

a) Serial processing

b) Parallel processing

c) delayed processing

In the 'content.xml' stream,

it is 'c)' the top parent element of display element.

In the 'settings.xml/styles.xml' stream,

it is 'b)' the top parent element of setting/style element.

And 'meta.xml', 'settings.xml', 'styles.xml', 'content.xml' It is serial processing.