Allow exporting state during e2e tests (#7860)

As of #7663, an in-memory store was used in place of local storage
during e2e tests, to facilitate the use of state fixtures. However,
this made it difficult to export state during a test run. The
instructions for exporting state to create fixtures assumed that local
storage was being used.

A new global function has been added to the background context to allow
exporting state. This method is available during testing and
development, and it works with either local storage or the in-memory
store. The fixture instructions have been updated to reference this new
function.

app/scripts/background.js

@@ -66,6 +66,10 @@ const localStore = inTest
   : new LocalStore()
 let versionedData
 
+if (inTest || process.env.METAMASK_DEBUG) {
+  global.metamaskGetState = localStore.get.bind(localStore)
+}
+
 // initialization flow
 initialize().catch(log.error)
 

test/e2e/fixtures/README.md

@@ -7,30 +7,17 @@ one thing:
 
 ## Generating fixture data
 
-Fixture data can be generated by loading the unpacked extension, inspecting the background context,
-dumping `chrome.storage.local`, and using [`copy`][1] to copy it to the clipboard, and manually pasting the contents into
-a file on disk.
+Fixture data can be generated by following these steps:
 
-```js
-// Step 1:
-chrome.storage.local.get(null, (x) => console.log(x))
-// Should print something like:
-// > temp1
-// > {data: {…}, meta: {…}}
+1. Load the unpacked extension in development or test mode
+2. Inspecting the background context of the extension
+3. Call `metamaskGetState`, then call [`copy`][1] on the results
 
-// Step 2:
-// Store the value as a global via the 'Store as global variable' option in context menu (shown below)
+You can then paste the contents directly in your fixture file.
 
-// Step 3:
-copy(temp1)
+```js
+copy(await metamaskGetState())
 ```
 
-Store the value as a global variable:
-
-<img
-  width="840"
-  alt="Store as global variable"
-  src="https://user-images.githubusercontent.com/1623628/60987884-1a2c4a00-a31d-11e9-932e-b7fab452e6bd.png"
-/>
 
   [1]:https://developers.google.com/web/tools/chrome-devtools/console/utilities