Cherry-pick from master: AAPT2: Fix JavaDoc first sentence extraction.

The old algorithm for detecting the first sentence of a JavaDoc comment
looked for the first occurence of '.'. This does not work when code or a
{@link android.R.styleable} link is encountered in the first sentence.

Switch to checking for whitespace characters after the '.' character.

Bug: 62900335
Test: make aapt2_tests , make ds-docs
Original change-Id: I8238f6a6304c9c2f92e2e576ca8962a59c2b20ea

Change-Id: Ie272d0d793d157f2a30f3ead20b2b53976661d33
diff --git a/tools/aapt2/text/Unicode.cpp b/tools/aapt2/text/Unicode.cpp
index 38ec9c4..75eeb46 100644
--- a/tools/aapt2/text/Unicode.cpp
+++ b/tools/aapt2/text/Unicode.cpp
@@ -66,6 +66,17 @@
   return FindCharacterProperties(codepoint) & CharacterProperties::kXidContinue;
 }
 
+// Hardcode the White_Space characters since they are few and the external/icu project doesn't
+// list them as data files to parse.
+// Sourced from http://www.unicode.org/Public/UCD/latest/ucd/PropList.txt
+bool IsWhitespace(char32_t codepoint) {
+  return (codepoint >= 0x0009 && codepoint <= 0x000d) || (codepoint == 0x0020) ||
+         (codepoint == 0x0085) || (codepoint == 0x00a0) || (codepoint == 0x1680) ||
+         (codepoint >= 0x2000 && codepoint <= 0x200a) || (codepoint == 0x2028) ||
+         (codepoint == 0x2029) || (codepoint == 0x202f) || (codepoint == 0x205f) ||
+         (codepoint == 0x3000);
+}
+
 bool IsJavaIdentifier(const StringPiece& str) {
   Utf8Iterator iter(str);