window.atob() returns wrong value when given a string container only white spaces

window.atob() returns wrong value when given a string container only white
spaces. The reason was that base64DecodeInternal() was calling Vector::grow()
before the loop but failed to call Vector::shrink() in case of early return.

R=
BUG=357332

Review URL: https://codereview.chromium.org/215833002

git-svn-id: svn://svn.chromium.org/blink/trunk@170264 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/fast/dom/Window/atob-btoa-expected.txt

@@ -49,6 +49,7 @@ PASS window.atob("zzz===") threw exception InvalidCharacterError: Failed to exec
 PASS window.atob("zzz====") threw exception InvalidCharacterError: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded..
 PASS window.atob("zzz=====") threw exception InvalidCharacterError: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded..
 PASS window.atob("zzzz") is "Ï<ó"
+PASS atob("            ") is ""
 PASS window.atob("zzzzz") threw exception InvalidCharacterError: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded..
 PASS window.atob("z=zz") threw exception InvalidCharacterError: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded..
 PASS window.atob("=") threw exception InvalidCharacterError: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded..

third_party/WebKit/LayoutTests/fast/dom/Window/atob-btoa.html

@@ -63,6 +63,7 @@ shouldThrow('window.atob("zzz===")'); // excess pad characters.
 shouldThrow('window.atob("zzz====")'); // excess pad characters.
 shouldThrow('window.atob("zzz=====")'); // excess pad characters.
 shouldBeEqualToString('window.atob("zzzz")', 'Ï\u003Có');
+shouldBeEqualToString('atob("            ")', ''); // whitespace only.
 shouldThrow('window.atob("zzzzz")');
 shouldThrow('window.atob("z=zz")');
 shouldThrow('window.atob("=")');

third_party/WebKit/Source/wtf/text/Base64.cpp

@@ -149,22 +149,34 @@ static inline bool base64DecodeInternal(const T* data, unsigned length, Vector<c
 
     unsigned equalsSignCount = 0;
     unsigned outLength = 0;
+    bool hadError = false;
     for (unsigned idx = 0; idx < length; ++idx) {
         unsigned ch = data[idx];
         if (ch == '=') {
             ++equalsSignCount;
             // There should never be more than 2 padding characters.
-            if (policy == Base64ValidatePadding && equalsSignCount > 2)
-                return false;
+            if (policy == Base64ValidatePadding && equalsSignCount > 2) {
+                hadError = true;
+                break;
+            }
         } else if (('0' <= ch && ch <= '9') || ('A' <= ch && ch <= 'Z') || ('a' <= ch && ch <= 'z') || ch == '+' || ch == '/') {
-            if (equalsSignCount)
-                return false;
+            if (equalsSignCount) {
+                hadError = true;
+                break;
+            }
             out[outLength++] = base64DecMap[ch];
         } else if (!shouldIgnoreCharacter || !shouldIgnoreCharacter(ch)) {
-            return false;
+            hadError = true;
+            break;
         }
     }
 
+    if (outLength < out.size())
+        out.shrink(outLength);
+
+    if (hadError)
+        return false;
+
     if (!outLength)
         return !equalsSignCount;