[Chrome,Safari] Improvements to HTMLElement.

[jpmedley]

• Items for Safari are from Confluence
• Here’s what was in Chrome 1. https://chromium.googlesource.com/chromium/src/+/b9679dc82ba724084429364f1422edc917772a2a/third_party/WebKit/WebCore/html/HTMLElement.idl
• Here’s the current state showing items I marked false: https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/html/html_element.idl?q=HTMLElement+f:.idl+file:%5Esrc/third_party/blink/renderer/+package:%5Echromium$&dr=C&l=21
• contextMenu was added in 45, here: https://storage.googleapis.com/chromium-find-releases-static/d92.html#d92527e8f6032374056532d57dd086eea859992c
• contextMenu was removed in 61, here: https://storage.googleapis.com/chromium-find-releases-static/e90.html#e90a0487386316a1e97f69159f20fbe5933cb3b9
• draggable is too old to be in Omaha Proxy, but its PR is July 14, 2009, which puts it in range for Chrome 7: https://chromium.googlesource.com/chromium/src/+/726e9fa405761cf5870266ed184da3812309e81b
• dropzone was removed in 59, here: https://storage.googleapis.com/chromium-find-releases-static/798.html#798a0d0b8b42492f3acd803caa2ce0b35b8b29d2
• dropzone is too old to be in Omaha Proxy, but its PR is May 27, 2011, which puts it in range for Chrome 14: https://chromium.googlesource.com/chromium/src/+/947f0135b2cd186d2d17e495ed1ea6a8d181697a
• I can find no evidence that forceSpellCheck is or ever has been supported.
• hidden is too old to be in Omaha Proxy, but its PR is June 24, 2010, which puts it in range for an extremely early version of Chrome.
• itemId, itemProp, itemRef itemScope, itemType, itemValue are too old to be in Omaha Proxy, but their Removal PR is April 12, 2013, which puts them in range for Chrome 28: https://chromium.googlesource.com/chromium/src/+/cafe0dbac468f3686a74aa4587909f1d9b442ed0
• itemId is too old to be in Omaha Proxy, but its PR is October 31, 2011, which puts it in range for Chrome 17: https://chromium.googlesource.com/chromium/src/+/8e5511d74bcb367fe6b2c3d87c95126b8b2b67da
• itemProp, itemRef, itemScope, itemType, itemValue are too old to be in Omaha Proxy, but their PR is October 25, 2011, which puts them in range for Chrome 17: https://chromium.googlesource.com/chromium/src/+/534b26ad510a61a360b3f5df52703f32523d7e3f
• translate was added on Feb 17, 2012, which puts it in range for Chrome 19: https://chromium.googlesource.com/chromium/src/+/a79c634d822b4fe74293d58884aeae7e8d7b1cf1
• autoCapitalize is in Chrome 66: https://storage.googleapis.com/chromium-find-releases-static/1de.html#1de83967752e0cf4f36f3a013b4f1ab687b88e11
• inputMode This shows that it was behind a flag called inputModeAttribute. This flag was set to stable in Chrome 66 https://storage.googleapis.com/chromium-find-releases-static/5ba.html#5ba5958247e67477d72d0b12d1b32ce557cbded6