This is a weird issue that I am only experiencing on a Native browser on Samsung Galaxy Tab 2 and Galaxy S2 in the native browser.
This has also been tested on othe
For double canvas issue there is a bug logged https://code.google.com/p/android/issues/detail?id=35474 you may want to check suggested solutions.
In my case this issue appeared only if I had Force GPU rendering enabled.
Issue usually appears if you have some parent element for canvas that has CSS overflow: hidden