Provide a web3 currentProvider shim for compatibility with snowtrace.io and staking.trava.finance

[srirambv]

Description

Wallet cannot connect to snowtrace.io ( Avalanche C-Chain explorer)

Steps to Reproduce

1. Go to https://snowtrace.io/tokenapprovalchecker
2. Enter a Wallet address
3. Click the Connect to Web 3 button on left
4. Select Metamask in popup window
5. The site returns another window that prompts you to Please connect your metamask
6. Then nothing happens, Brave Wallet cannot connect to Web3 Metamask feature for https://snowtrace.io/

Actual result:

Expected result:

Should connect to Dapp

Reproduces how often:

Easy

Brave version (brave://version info)

Brave	1.36.11 Chromium: 97.0.4692.56 (Official Build) nightly (arm64)
Revision	04da6c66398ca50e603cc236a07dc7dfd3bbc750-refs/branch-heads/4692@{#990}
OS	macOS Version 12.1 (Build 21C52)

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• Can you reproduce this issue with the beta channel? Yes
• Can you reproduce this issue with the nightly channel? Yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? NA
• Does the issue resolve itself when disabling Brave Rewards? NA
• Is the issue reproducible on the latest version of Chrome? NA

Miscellaneous Information:

cc: @bbondy

QA tests

1. Do the above
2. Try to connect on staking.trava.finance, it should no longer give a provider error.

[bbondy]

thanks for the ping, I'll take a look

[bbondy]

It's because they're using window.web3.currentProvider and wallets should not provide window.web3 anymore.

I tweeted at them here and hopefully someone there sees it.
https://twitter.com/brianbondy/status/1479124596456624144

I also asked MM to actually get rid of the web3 shim they inject.
For transparency, that message was:

Are you guys planning to remove window.web3 shim anytime soon? We haven’t included one in the new Brave Wallet and have only ran into 1 issue so far with snowtrace.io which uses window.web3.currentProvider instead of using window.ethereum
I’d rather not pollute the global namespace and add support for Dapp compat for it. But I might have to if there’s no plans to actually deprecate window.web3 from MetaMask’s end.

[srirambv]

Brave	1.35.98 Chromium: 98.0.4758.72 (Official Build) (64-bit)
Revision	d0fe1ec4df090cd3eb02b591228505e12ea476e9-refs/branch-heads/4758@{#935}
OS	☑️ Linux	☑️ Windows 11 Version Dev (Build 22523.1000)	☑️ macOS Version 12.0.1 (Build 21C52)
Verified steps from issue description Verified able to connect without errors on both https://staking.trava.finance and https://staking.trava.finance
https://snowtrace.io/	20353-Linux.mp4	20353-Windows.mov	20353-macOS.mov
https://staking.trava.finance	20353-Linux.mp4	20353-Windows.mov	20353-macOS.mov