[clang-format] Indent import statements in JavaScript.

[clang-format] Indent import statements in JavaScript.

Take for example this piece of code found at
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import>.

```
for (const link of document.querySelectorAll("nav > a")) {
  link.addEventListener("click", e => {
    e.preventDefault();

    import('/modules/my-module.js')
        .then(module => {
          module.loadPageInto(main);
        })
        .catch(err => {
          main.textContent = err.message;
        });
  });
}
```

Previously the import line would be unindented, looking like this.

```
for (const link of document.querySelectorAll("nav > a")) {
  link.addEventListener("click", e => {
    e.preventDefault();

import('/modules/my-module.js')
        .then(module => {
          module.loadPageInto(main);
        })
        .catch(err => {
          main.textContent = err.message;
        });
  });
}
```

Actually we were going to fix this along with fixing Verilog import
statements.  But the patch got too big.

Reviewed By: MyDeveloperDay, curdeius

Differential Revision: https://reviews.llvm.org/D121906

Author: eywdck2l

clang/lib/Format/UnwrappedLineFormatter.cpp

@@ -1431,8 +1431,10 @@ void UnwrappedLineFormatter::formatFirstToken(
   if (Newlines)
     Indent = NewlineIndent;
 
-  // Preprocessor directives get indented before the hash only if specified
-  if (Style.IndentPPDirectives != FormatStyle::PPDIS_BeforeHash &&
+  // Preprocessor directives get indented before the hash only if specified. In
+  // Javascript import statements are indented like normal statements.
+  if (!Style.isJavaScript() &&
+      Style.IndentPPDirectives != FormatStyle::PPDIS_BeforeHash &&
       (Line.Type == LT_PreprocessorDirective ||
        Line.Type == LT_ImportStatement))
     Indent = 0;

clang/unittests/Format/FormatTestJS.cpp

@@ -1875,6 +1875,11 @@ TEST_F(FormatTestJS, Modules) {
                                               " myX} from 'm';");
   verifyFormat("import * as lib from 'some/module.js';");
   verifyFormat("var x = {import: 1};\nx.import = 2;");
+  // Ensure an import statement inside a block is at the correct level.
+  verifyFormat("function() {\n"
+               "  var x;\n"
+               "  import 'some/module.js';\n"
+               "}");
 
   verifyFormat("export function fn() {\n"
                "  return 'fn';\n"