Omit blank lines after imports in package-info files

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=157895967

Author: cushon

core/src/main/java/com/google/googlejavaformat/java/ImportOrderer.java

@@ -22,6 +22,8 @@
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.googlejavaformat.Newlines;
 import com.google.googlejavaformat.java.JavaInput.Tok;
+import java.util.ArrayList;
+import java.util.List;
 import org.openjdk.tools.javac.parser.Tokens.TokenKind;
 
 /** Orders imports in Java source code. */
@@ -115,27 +117,26 @@ private String reorderImports() throws FormatterException {
       throw new FormatterException("Imports not contiguous (perhaps a comment separates them?)");
     }
 
-    // Add back the text from after the point where we stopped tokenizing.
-    String tail;
-    if (toks.isEmpty()) {
-      tail = "";
-    } else {
-      Tok lastTok = getLast(toks);
-      int tailStart = lastTok.getPosition() + lastTok.length();
-      tail = text.substring(tailStart);
-    }
-
     StringBuilder result = new StringBuilder();
     result.append(
         CharMatcher.whitespace().trimTrailingFrom(tokString(0, unindentedFirstImportStart)));
     if (result.length() > 0) {
       result.append(lineSeparator).append(lineSeparator);
     }
     result.append(reorderedImportsString(imports.imports));
-    result.append(lineSeparator);
-    result.append(
-        CharMatcher.whitespace().trimLeadingFrom(tokString(afterLastImport, toks.size())));
-    result.append(tail);
+
+    List<String> tail = new ArrayList<>();
+    tail.add(CharMatcher.whitespace().trimLeadingFrom(tokString(afterLastImport, toks.size())));
+    if (!toks.isEmpty()) {
+      Tok lastTok = getLast(toks);
+      int tailStart = lastTok.getPosition() + lastTok.length();
+      tail.add(text.substring(tailStart));
+    }
+    if (tail.stream().anyMatch(s -> !s.isEmpty())) {
+      result.append(lineSeparator);
+      tail.forEach(result::append);
+    }
+
     return result.toString();
   }
 

core/src/test/java/com/google/googlejavaformat/java/MainTest.java

@@ -254,4 +254,26 @@ public void importRemoveErrorParseError() throws Exception {
     assertThat(main.format("-")).isEqualTo(1);
     assertThat(err.toString()).contains("<stdin>:4:3: error: class, interface, or enum expected");
   }
+
+  @Test
+  public void packageInfo() throws Exception {
+    String[] input = {
+      "@CheckReturnValue",
+      "@ParametersAreNonnullByDefault",
+      "package com.google.common.labs.base;",
+      "",
+      "import javax.annotation.CheckReturnValue;",
+      "import javax.annotation.ParametersAreNonnullByDefault;",
+      "",
+    };
+    StringWriter out = new StringWriter();
+    StringWriter err = new StringWriter();
+    Main main =
+        new Main(
+            new PrintWriter(out, true),
+            new PrintWriter(err, true),
+            new ByteArrayInputStream(joiner.join(input).getBytes(UTF_8)));
+    assertThat(main.format("-")).isEqualTo(0);
+    assertThat(out.toString()).isEqualTo(joiner.join(input));
+  }
 }