Switching theme doesn't update CW page

[srirambv]

Description

Switching theme doesn't update CW page

Steps to Reproduce

1. Set browser theme to dark
2. Load 0.1.37 component
3. Ensure Dark theme is used for CW
4. Switch browser theme to light
5. CW doesn't change theme need to reload page to switch to light

Actual result:

Switching theme doesn't update CW page

Expected result:

Should auto switch

Reproduces how often:

Easy with compoent sideload

Brave version (brave://version info)

Component 0.1.37

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 dev 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:

Switching from light to dark works fine but dark to light doesn't. May also need to test this after component is released

[srirambv]

Verification passed on

Brave	1.5.76 Chromium: 80.0.3987.66 (Official Build) nightly (64-bit)
Revision	56ea77d65c47ecbb1180b99f860d85b51117864a-refs/branch-heads/3987@{#662}
OS	Linux
Component	0.1.41

• Verified switching theme from settings automatically updates CW page as well
  

---

Verification passed on

Brave	1.6.14 Chromium: 80.0.3987.87 (Official Build) nightly (64-bit)
Revision	449cb163497b70dbf98d389f54e38e85d4c59b43-refs/branch-heads/3987@{#801}
OS	Windows 10 OS Version 1803 (Build 17134.523)
Component	0.1.42

• Verified switching theme from settings automatically updates CW page as well
  

---

Verification passed on

Brave	1.6.14 Chromium: 80.0.3987.87 (Official Build) nightly (64-bit)
Revision	449cb163497b70dbf98d389f54e38e85d4c59b43-refs/branch-heads/3987@{#801}
OS	macOS Version 10.15.1 (Build 19B88)
Component	0.1.42

• Verified switching theme from settings automatically updates CW page as well