File constructor understands lastModified.

LayoutTests/fast/files/file-constructor.html

Index: LayoutTests/fast/files/file-constructor.html
diff --git a/LayoutTests/fast/files/file-constructor.html b/LayoutTests/fast/files/file-constructor.html
index f615864f75e496d559deab8828f0874b669cf0b7..5985d524c43f6a0788780afe8f29b5c6f25d2fe8 100644
--- a/LayoutTests/fast/files/file-constructor.html
+++ b/LayoutTests/fast/files/file-constructor.html
@@ -69,6 +69,9 @@ shouldThrow("new File([], 'world.html', {endings:'illegalValue'})", "'TypeError:
 shouldThrow("new File([], 'world.html', {endings:throwingObj})", "'Error'");
 shouldThrow("new File([], 'world.html', {type:throwingObj})", "'Error'");
 shouldThrow("new File([], 'world.html', {type:'hello\u00EE'})", "'SyntaxError: Failed to construct \\'File\\': The \"type\" property must consist of ASCII characters.'");
+shouldThrow("new File([], 'world.html', {lastModifiedDate: 'not a date'})", "'TypeError: Failed to construct \\'File\\': The \"lastModifiedDate\" property must be a Date instance.'");
+shouldThrow("new File([], 'world.html', {lastModifiedDate: null})", "'TypeError: Failed to construct \\'File\\': The \"lastModifiedDate\" property must be a Date instance.'");
+shouldThrow("new File([], 'world.html', {lastModifiedDate: Date.now()})", "'TypeError: Failed to construct \\'File\\': The \"lastModifiedDate\" property must be a Date instance.'");
 
 // Test various non-object literals being used as property bags.
 shouldThrow("(new File([], 'world.html', null)) instanceof window.File", "'TypeError: Failed to construct \\'File\\': The 3rd argument is not of type Object.'");
@@ -87,6 +90,21 @@ shouldBe("(new File([], 'world.html', {type:'text/html'})).type", "'text/html'")
 shouldBe("(new File([], 'world.html', {type:'text/html'})).size", "0");
 shouldBe("(new File([], 'world.html', {type:'text/plain;charset=UTF-8'})).type", "'text/plain;charset=utf-8'");
 
+// Test that the lastModificationDate is correctly added to the File.
+var aDate = new Date(441532800000);
+shouldBeTrue("(new File([], 'world.html', {lastModifiedDate: aDate})).lastModifiedDate instanceof Date");
+shouldBe("(new File([], 'world.html', {lastModifiedDate: aDate})).lastModifiedDate.valueOf()", "aDate.valueOf()");
+shouldBeTrue("(new File([], 'world.html', {lastModifiedDate: new Date(NaN)})).lastModifiedDate instanceof Date");
+shouldBeNaN("(new File([], 'world.html', {lastModifiedDate: new Date(NaN)})).lastModifiedDate.valueOf()");
+// Unless specified, lastModifiedDate should default to now.
+shouldBeTrue("(new File([], 'world.html')).lastModifiedDate instanceof Date");
+var startTime = Date.now();
+var fileTime = (new File([], 'world.html')).lastModifiedDate.valueOf();
+var endTime = Date.now();
+// FIXME: these checks will fail if time goes backwards, e.g. DST. We should have a generic bullet-proof method for comparing against Date.now().

[jsbell, 2013/11/18 20:54:05]

Drive-by comment:

Date.now() is ms since epoch in UTC, so there should be no DST issue.

Things like the clock on the machine being reset by NTP or user action could
affect the value, though. 

[pwnall-personal, 2013/11/19 09:10:12]

Thank you very much for pointing this out!

I updated the comment and the CL I put together for making this more robust.
https://codereview.chromium.org/69813015

+shouldBeTrue("startTime <= fileTime");
+shouldBeTrue("fileTime <= endTime");
+
 // Test the number of expected arguments in the File constructor.
 shouldBe("window.File.length", "2");