Fix RGBA alpha parsing and serialization to adhere to W3 standard.

third_party/WebKit/Source/web/tests/WebViewTest.cpp

Index: third_party/WebKit/Source/web/tests/WebViewTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/WebViewTest.cpp b/third_party/WebKit/Source/web/tests/WebViewTest.cpp
index 0840d8c1b77fabff9833895c78e37f803c92c267..4bb2739ec73b879b1c68b087f7de6cbd5437d727 100644
--- a/third_party/WebKit/Source/web/tests/WebViewTest.cpp
+++ b/third_party/WebKit/Source/web/tests/WebViewTest.cpp
@@ -394,11 +394,11 @@ TEST_P(WebViewTest, SetBaseBackgroundColor) {
                                    "style></head></html>",
                                    baseURL);
   // Expected: red (50% alpha) blended atop base of kBlue.
-  EXPECT_EQ(0xFF7F0080, webView->backgroundColor());
+  EXPECT_EQ(0xFF80007F, webView->backgroundColor());

[sashab, 2017/01/02 23:04:16]

Why change these tests? Also what is 0xFF80007F -- can we get rid of this magic
constant?

[ktyliu, 2017/01/03 02:14:22]

0xFF80007F is the expected result of layering 50% of red -- rgba(255,0,0,0.5) on
top of solid blue -- rgb(0,0,255)

the test needs to be fixed because original implementation of alpha value
resulted in 50% of red 255 on red 0 here becoming 0x7F (127) rather than the
correct value of 0x80 (128)

similarly, overlaying the blue value of 0 with 50% alpha on top of pure blue
background should reduce blue 255 down to blue 127 rather than 128

 
   webView->setBaseBackgroundColor(kTranslucentPutty);
   // Expected: red (50% alpha) blended atop kTranslucentPutty. Note the alpha.
-  EXPECT_EQ(0xBFE93B32, webView->backgroundColor());
+  EXPECT_EQ(0xBFE93A31, webView->backgroundColor());
 
   webView->setBaseBackgroundColor(kTransparent);
   FrameTestHelpers::loadHTMLString(webView->mainFrame(),