Don't throw an exception when accessing local,sessionStorage in 3p frame

[pes10k]

Currently, Chromium throws an exception when JS just touches window.{local,session}Storage, which prevents sites from doing typical feature detection style checks. We should just act as if these values aren't present (e.g. window.localStorage === undefined|null) so that defensive / well programmed sites still work correctly

[pes10k]

This is related to #8514

[iefremov]

Should be resolved in brave/brave-core#5533

[LaurenWags]

@pes10k @iefremov @bridiver could we get a test plan for this one please? If no manual QA is required, let's change the label to QA/No. Thanks! cc @rebron @kjozwiak

[pes10k]

Hi @LaurenWags , i just added tests for this at https://dev-pages.brave.software/storage/exceptions.html. I think the text there explains the cases, but as long as the "received" column matches the "expected" column when shields are up, then it should be golden

[LaurenWags]

Thanks @pes10k!

Verified passed with

Brave | 1.12.105 Chromium: 84.0.4147.105 (Official Build) (64-bit)
-- | --
Revision | a6b12dfad6663f13a7e16e9a42a6a4975374096b-refs/branch-heads/4147@{#943}
OS | macOS Version 10.14.6 (Build 18G3020)

• Verified test plan from Don't throw an exception when accessing local,sessionStorage in 3p frame #9758 (comment)
• Confirmed with default shields the received column value matches the expected column value on https://dev-pages.brave.software/storage/exceptions.html

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Verification passed on

Brave | 1.12.105 Chromium: 84.0.4147.105 (Official Build) (64-bit)
-- | --
Revision | a6b12dfad6663f13a7e16e9a42a6a4975374096b-refs/branch-heads/4147@{#943}
OS | Windows 10 OS Version 1903 (Build 18362.959)

• Verified test plan from Don't throw an exception when accessing local,sessionStorage in 3p frame #9758 (comment)
• Confirmed with default shields the received column value matches the expected column value on https://dev-pages.brave.software/storage/exceptions.html
  

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Verification passed on

Brave	1.12.105 Chromium: 84.0.4147.105 (Official Build) (64-bit)
Revision	a6b12dfad6663f13a7e16e9a42a6a4975374096b-refs/branch-heads/4147@{#943}
OS	Ubuntu 18.04 LTS

• Verified test plan from Don't throw an exception when accessing local,sessionStorage in 3p frame #9758 (comment)
• Confirmed with default shields the received column value matches the expected column value on https://dev-pages.brave.software/storage/exceptions.html
  

[srirambv]

Verification passed on Samsung Tab A with Android 10 running 1.12.111 x64 build

• Verified test plan Don't throw an exception when accessing local,sessionStorage in 3p frame #9758 (comment)
• Verified with default shields settings expected and received` values match
  

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Verification passed on OnePlus 6T with Android 10 running 1.12.111 x64 build

• Verified test plan Don't throw an exception when accessing local,sessionStorage in 3p frame #9758 (comment)
• Verified with default shields settings expected and received` values match