Bring back paste button hide behavior 2

[justinmc]

Original PR that has been reverted twice now: #54902

This caused a failure where the ClipboardStatusNotifier was modified after being disposed, which seems to be caused by receiving the clipboard data after disposal. My one line fix for this is to check if it's disposed before updating the value.

[goderbauer]

LGTM

[goderbauer]

Let's move the if (_disposed) check to be the first thing in this callback since we don't have to do any of the other work if that happens.

[justinmc]

Smart, will do.

[jmagman]

I believe this causes a new failure:

2020-05-11T14:41:55.457819: stdout: [+1992 ms] 00:09 �[32m+0�[0m�[31m -1�[0m: AccessibilityBridge TextField TextField has correct Android semantics �[1m�[31m[E]�[0m�[0m
2020-05-11T14:41:55.457984: stdout: [        ]   Expected: AndroidSemanticsNode with className: android.widget.EditText with actions: [AndroidSemanticsAction.clearAccessibilityFocus, AndroidSemanticsAction.click, AndroidSemanticsAction.setSelection] with flag isEditable: true with flag isFocusable: true with flag isFocused: true with flag isPassword: false
2020-05-11T14:41:55.458259: stdout: [        ]     Actual: AndroidSemanticsNode:<{flags: {isEditable: true, isEnabled: true, isDismissable: false, isCheckable: false, isChecked: false, isFocused: true, isLongClickable: false, isFocusable: true, isPassword: false}, id: 14, text: null, rect: {height: 144, width: 1080, bottom: 128.0, top: 80.0, left: 0.0, right: 360.0}, actions: [131072, 32768, 16, 128], className: android.widget.EditText, liveRegion: 1, contentDescription: null}>
2020-05-11T14:41:55.458442: stdout: [        ]      Which: Expected actions: [AndroidSemanticsAction.clearAccessibilityFocus, AndroidSemanticsAction.click, AndroidSemanticsAction.setSelection]
2020-05-11T14:41:55.458710: stdout: [        ]             Actual actions: [AndroidSemanticsAction.clearAccessibilityFocus, AndroidSemanticsAction.click, AndroidSemanticsAction.copy, AndroidSemanticsAction.setSelection]
2020-05-11T14:41:55.458935: stdout: [        ]             Unexpected: {AndroidSemanticsAction.copy}
2020-05-11T14:41:55.459211: stdout: [        ]             Missing: {}

android_semantics_integration_test_d988226_2.log