migrate fp site settings when fp has not been toggled globally

fix #12497 by doing the site settings migration even when fingerprinting protection's global setting has not been changed.

Test Plan:
1. in a fresh 0.19.x profile, go to any website and enable fingerprinting protection on it
2. now update to 0.20.x or later
3. re-open brave and go to the website from step 1
4. open page shields. it should say 'block all fingerprinting'.

app/sessionStore.js

@@ -835,10 +835,9 @@ module.exports.runPreMigrations = (data) => {
   return data
 }
 
-module.exports.runPostMigrations = (immutableData) => {
-  const globalFpSetting = immutableData.getIn(['settings', 'privacy.block-canvas-fingerprinting'])
-  // fingerprinting protection migration
-  if (typeof globalFpSetting !== 'boolean') {
+// 0.19.x -> 0.20.x fingerprinting protection migration
+const fingerprintingProtectionMigration = (immutableData) => {
+  if (immutableData.get('fingerprintingProtectionAll')) {
     return immutableData
   }
   try {
@@ -853,6 +852,7 @@ module.exports.runPostMigrations = (immutableData) => {
         return setting
       })
     immutableData = immutableData.set('siteSettings', siteSettings)
+    const globalFpSetting = !!immutableData.getIn(['settings', 'privacy.block-canvas-fingerprinting'])
     immutableData = immutableData.setIn(['fingerprintingProtectionAll', 'enabled'],
       globalFpSetting).deleteIn(['settings', 'privacy.block-canvas-fingerprinting'])
   } catch (e) {
@@ -861,6 +861,11 @@ module.exports.runPostMigrations = (immutableData) => {
   return immutableData
 }
 
+module.exports.runPostMigrations = (immutableData) => {
+  immutableData = fingerprintingProtectionMigration(immutableData)
+  return immutableData
+}
+
 module.exports.runImportDefaultSettings = (data) => {
   // import default site settings list
   if (!data.defaultSiteSettingsListImported) {

test/unit/app/sessionStoreTest.js

@@ -1742,6 +1742,47 @@ describe('sessionStore unit tests', function () {
   })
 
   describe('runPostMigrations', function () {
-    // TODO:
+    describe('when `fingerprintingProtectionAll` is set', function () {
+      it('does not modify anything', function () {
+        let exampleState = Immutable.fromJS(sessionStore.defaultAppState())
+        exampleState = exampleState.set('fingerprintingProtectionAll', {enabled: false})
+        const returnedAppState = sessionStore.runPostMigrations(exampleState)
+        assert.equal(returnedAppState, exampleState)
+      })
+    })
+
+    describe('when `fingerprintingProtectionAll` is not set', function () {
+      describe('when `fingerprintingProtection` is `true` for a site', function () {
+        it('updates to a text status of `blockAllFingerprinting`', function () {
+          let exampleState = Immutable.fromJS(sessionStore.defaultAppState())
+          exampleState = exampleState.setIn(['siteSettings', 'example.com', 'fingerprintingProtection'], true)
+          const returnedAppState = sessionStore.runPostMigrations(exampleState)
+          assert.equal(returnedAppState.getIn(['siteSettings', 'example.com', 'fingerprintingProtection']), 'blockAllFingerprinting')
+        })
+      })
+
+      describe('when `fingerprintingProtection` is `false` for a site', function () {
+        it('updates to a text status of `allowAllFingerprinting`', function () {
+          let exampleState = Immutable.fromJS(sessionStore.defaultAppState())
+          exampleState = exampleState.setIn(['siteSettings', 'example.com', 'fingerprintingProtection'], false)
+          const returnedAppState = sessionStore.runPostMigrations(exampleState)
+          assert.equal(returnedAppState.getIn(['siteSettings', 'example.com', 'fingerprintingProtection']), 'allowAllFingerprinting')
+        })
+      })
+
+      it('sets a new global fingerprinting value (based on existing value truthy-ness)', function () {
+        let exampleState = Immutable.fromJS(sessionStore.defaultAppState())
+        exampleState = exampleState.setIn(['settings', 'privacy.block-canvas-fingerprinting'], 'EXAMPLE TRUTHY VALUE')
+        const returnedAppState = sessionStore.runPostMigrations(exampleState)
+        assert.equal(returnedAppState.getIn(['fingerprintingProtectionAll', 'enabled']), true)
+      })
+
+      it('deletes the old global fingerprinting value', function () {
+        let exampleState = Immutable.fromJS(sessionStore.defaultAppState())
+        exampleState = exampleState.setIn(['settings', 'privacy.block-canvas-fingerprinting'], true)
+        const returnedAppState = sessionStore.runPostMigrations(exampleState)
+        assert.equal(returnedAppState.getIn(['siteSettings', 'privacy.block-canvas-fingerprinting']), undefined)
+      })
+    })
   })
 })