Screenshot generation stops when encountering an unsupported background-image function

[val1984]

• You are using the latest version
• You are testing using the non-minified version of html2canvas and checked any potential issues reported in the console

Bug reports:

When trying to generate a screenshot where an unsupported background-image function such as repeating-linear-gradient, screenshot generation does not complete and gives the following error:

Could not generate screenshot for help request Error: Attempting to parse an unsupported image function "repeating-linear-gradient"
    at parse (html2canvas.js:2834)
    at Array.map (<anonymous>)
    at Object.parse (html2canvas.js:2868)
    at parse (html2canvas.js:4114)
    at new CSSParsedDeclaration (html2canvas.js:3998)
    at new ElementContainer (html2canvas.js:4138)
    at createContainer (html2canvas.js:4485)
    at parseNodeTree (html2canvas.js:4438)
    at parseNodeTree (html2canvas.js:4451)
    at parseNodeTree (html2canvas.js:4451)

Whereas in 1.0.0-rc.1 and earlier, it didn't stop screenshot generation.
Example: http://jsfiddle.net/yh4L67bf/
The error is thrown from here:

html2canvas/src/css/types/image.ts

Line 92 in 522a443

throw new Error(`Attempting to parse an unsupported image function "${value.name}"`);

Specifications:

• html2canvas version tested with: 1.0.0-rc.3
• Browser & version: Google Chrome 74.0.3729.169
• Operating system: Windows 10