Uses WTF::String::Number instead of WTF::String::format in CSSPrimitiveValue::CustomCSSText. #15830
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…veValue::CustomCSSText. CSSPrimitiveValue::CustomCSSText can be called huge amount of times through InspectorDOMSnapshotAgent::getSnapshot. It underlyingly calls WTF::String::format which is sort of expensive by considering the huge call volume. Actually CustomCSSText only needs to convert number to string. And WTF::String provides a cheaper way, String::Number, to achieve same goal. WTF::String uses WTF Dtoa function to mimic "%.[precision]g" format. According to C11 standard (http://port70.net/~nsz/c/c11/n1570.html#7.21.6), when using "%[.percisiong]g" format, (1) The exponent always contains at least two digits, and only as many more digits as necessary to represent the exponent. If the value is zero, the exponent is zero. (2) Finally, unless the # flag is used, any trailing zeros are removed from the fractional portion of the result and the decimal-point character is removed if there is no fractional portion remaining. But the WTF Dota function doesn't comply with the rules. Fix it in this change. Change-Id: I896981f54aa0e327c85d6bc4cb87dd9a0291e124
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Close this PR because the Chromium CL does not have exportable changes. |
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CSSPrimitiveValue::CustomCSSText can be called huge amount of times
through InspectorDOMSnapshotAgent::getSnapshot. It underlyingly calls
WTF::String::format which is sort of expensive by considering the huge
call volume.
Actually CustomCSSText only needs to convert number to string. And
WTF::String provides a cheaper way, String::Number, to achieve same
goal.
WTF::String uses WTF Dtoa function to mimic "%.[precision]g" format. According to C11 standard
(http://port70.net/~nsz/c/c11/n1570.html#7.21.6), when using "%[.percisiong]g" format,
(1) The exponent always contains at least two digits, and only as many more digits as
necessary to represent the exponent. If the value is zero, the exponent is zero.
(2) Finally, unless the # flag is used, any trailing zeros are removed from the
fractional portion of the result and the decimal-point character is removed if there
is no fractional portion remaining.
But the WTF Dota function doesn't comply with the rules. Fix it in this change.
Change-Id: I896981f54aa0e327c85d6bc4cb87dd9a0291e124
Reviewed-on: https://chromium-review.googlesource.com/1512138
WPT-Export-Revision: ad2ac74a96a48d2f22205190b48a0f66775ad7d9