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
Change-Id: I8238f6a6304c9c2f92e2e576ca8962a59c2b20ea

tools/aapt2/java/AnnotationProcessor.cpp

@@ -18,12 +18,29 @@
 
 #include <algorithm>
 
+#include "text/Unicode.h"
+#include "text/Utf8Iterator.h"
 #include "util/Util.h"
 
-using android::StringPiece;
+using ::aapt::text::Utf8Iterator;
+using ::android::StringPiece;
 
 namespace aapt {
 
+StringPiece AnnotationProcessor::ExtractFirstSentence(const StringPiece& comment) {
+  Utf8Iterator iter(comment);
+  while (iter.HasNext()) {
+    const char32_t codepoint = iter.Next();
+    if (codepoint == U'.') {
+      const size_t current_position = iter.Position();
+      if (!iter.HasNext() || text::IsWhitespace(iter.Next())) {
+        return comment.substr(0, current_position);
+      }
+    }
+  }
+  return comment;
+}
+
 void AnnotationProcessor::AppendCommentLine(std::string& comment) {
   static const std::string sDeprecated = "@deprecated";
   static const std::string sSystemApi = "@SystemApi";