Fix ResourceLoadTiming resolution lose issue.

Currently, WebCore::ResourceLoadTiming has a base requestTime with type "double", others are millisecond 
deltas with type "int", it forces following timestamps align with the base time, such as dnsStart. 
So in glue(webkit/glue/, we had to calculate delta between the real dnsStart and 
its base time request_start, round to a int value in millisecond, while, lose the resolution. It may cause
timestamps overlap or tricky negative values.
This change removes all "int" deltas and use monotonicallyIncreasing "double" in second instead.

To satisfy test result, we need to add new fields in blink and then switch chrome use the new fields, at last go back blink to remove old fields. This change is the first step and use a macro to guard the new added field.

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git-svn-id: svn:// bbb929c8-8fbe-4397-9dbb-9b2b20218538
9 files changed