Currently, attribute and child arrays (implemented in dom/base/nsAttrAndChildArray.h) start out empty. When cloning, the array ends up being resized multiple times in order to add the attributes and children that are being cloned from the original node. This would be quicker if the array was initialized to the correct size in the first place so that resizes are not necessary.
However, preallocating space for children is only necessary when performing a deep clone. Therefore, an additional parameter is being added to the Clone, CopyInnerTo, and CloneDocHelper methods to indicate whether preallocation of children should happen. Attributes are copied either way, so that part of the array is preallocated in both cases.
MozReview-Commit-ID: 3iVezeAKXnI
The user can switch to the main <summary> by tab key, and toggle the
<details> by either 'space' key or 'enter' key.
'return' key is handled with 'keypress', and the 'space' key is handled
with 'keyup' like the HTMLInputElement.
MozReview-Commit-ID: HE6IduUGCpj
