Update the API documentations with Paul review comments.

pkg/analyzer/lib/src/dart/analysis/byte_store.dart

Index: pkg/analyzer/lib/src/dart/analysis/byte_store.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/byte_store.dart b/pkg/analyzer/lib/src/dart/analysis/byte_store.dart
index b852380946efe46c3be754ac39cf03c3397d6b12..698b5666a09911fd705b61dc57c2e9c4a6631ea7 100644
--- a/pkg/analyzer/lib/src/dart/analysis/byte_store.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/byte_store.dart
@@ -7,8 +7,11 @@ import 'dart:collection';
 /**
  * Store of bytes associated with string keys.
  *
+ * Each key must be not longer than 100 characters and consist of only `[a-z]`,
+ * `[0-9]`, `.` and `_` characters. It cannot have the sequence `..` in it.

[Paul Berry, 2016/10/23 21:10:18]

Two other constraints:
- the key can't be the literal string "."
- the key can't be the empty string

+ *
  * Note that associations are not guaranteed to be persistent. The value
- * associated with a key can change or become `null` at any point of time.
+ * associated with a key can change or become `null` at any point in time.
  */
 abstract class ByteStore {
   /**
@@ -24,7 +27,9 @@ abstract class ByteStore {
 }
 
 /**
- * [ByteStore] with LRU cache.
+ * A wrapper around [ByteStore] which adds an in-memory LRU cache to it.
+ *
+ * TODO(scheglov) Consider implementing size and/or time eviction policies.
  */
 class MemoryCachingByteStore implements ByteStore {
   final ByteStore store;