NOT FOR LANDING: Hack up CSSParser for speed.

third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp

Index: third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp
diff --git a/third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp b/third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp
index 888ca97a67c350195d18c12fb2b5fbb94bf19434..d7ca2b8201c6efe8c28b5ad41e599f9e4a43c943 100644
--- a/third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp
+++ b/third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp
@@ -86,6 +86,125 @@ StringToUnitTable& unitTable()
     return unitTable;
 }
 
+template<typename CharacterType>
+CSSPrimitiveValue::UnitType toUnitType(CharacterType* chars, unsigned length)

[esprehn, 2016/04/22 23:30:57]

This was a very big improvement, it skips malloc of the String and the hash
table lookup.

+{
+    switch (length) {
+    case 0:
+        return CSSPrimitiveValue::UnitType::UserUnits;
+    case 1:
+        if (toASCIILower(chars[0]) == 's')

[Timothy Loh, 2016/04/27 06:52:05]

toASCIILowerUnchecked or isASCIIAlphaCaselessEqual (I'm not sure why this
function has a LIKELY)

+            return CSSPrimitiveValue::UnitType::Seconds;
+        break;
+    case 2:
+        switch (toASCIILower(chars[0])) {
+        case 'c':
+            switch (toASCIILower(chars[1])) {
+            case 'h':
+                return CSSPrimitiveValue::UnitType::Chs;
+            case 'm':
+                return CSSPrimitiveValue::UnitType::Centimeters;
+            }
+            break;
+        case 'e':
+            switch (toASCIILower(chars[1])) {
+            case 'm':
+                return CSSPrimitiveValue::UnitType::Ems;
+            case 'x':
+                return CSSPrimitiveValue::UnitType::Exs;
+            }
+            break;
+        case 'f':
+            if (toASCIILower(chars[0]) == 'r')
+                return CSSPrimitiveValue::UnitType::Fraction;
+            break;
+        case 'h':
+            if (toASCIILower(chars[0]) == 'z')
+                return CSSPrimitiveValue::UnitType::Hertz;
+            break;
+        case 'i':
+            if (toASCIILower(chars[0]) == 'n')
+                return CSSPrimitiveValue::UnitType::Inches;
+            break;
+        case 'm':
+            switch (toASCIILower(chars[1])) {
+            case 'm':
+                return CSSPrimitiveValue::UnitType::Millimeters;
+            case 's':
+                return CSSPrimitiveValue::UnitType::Milliseconds;
+            }
+            break;
+        case 'p':
+            switch (toASCIILower(chars[1])) {
+            case 'c':
+                return CSSPrimitiveValue::UnitType::Picas;
+            case 't':
+                return CSSPrimitiveValue::UnitType::Points;
+            case 'x':
+                return CSSPrimitiveValue::UnitType::Pixels;
+            }
+            break;
+        case 'v':
+            switch (toASCIILower(chars[1])) {
+            case 'h':
+                return CSSPrimitiveValue::UnitType::ViewportHeight;
+            case 'w':
+                return CSSPrimitiveValue::UnitType::ViewportWidth;
+            }
+            break;
+        }
+        break;
+    case 3:
+        switch (toASCIILower(chars[0])) {
+        case 'd':
+            switch (toASCIILower(chars[1])) {
+            case 'e':
+                if (toASCIILower(chars[2]) == 'g')
+                    return CSSPrimitiveValue::UnitType::Degrees;
+                break;
+            case 'p':
+                if (toASCIILower(chars[2]) == 'i')
+                    return CSSPrimitiveValue::UnitType::DotsPerInch;
+                break;
+            }
+            break;
+        case 'k':
+            if (toASCIILower(chars[1]) == 'h' && toASCIILower(chars[2]) == 'z')
+                return CSSPrimitiveValue::UnitType::Kilohertz;
+            break;
+        case 'r':
+            switch (toASCIILower(chars[1])) {
+            case 'a':
+                if (toASCIILower(chars[2]) == 'd')
+                    return CSSPrimitiveValue::UnitType::Radians;
+                break;
+            case 'e':
+                if (toASCIILower(chars[2]) == 'm')
+                    return CSSPrimitiveValue::UnitType::Rems;
+                break;
+            }
+            break;
+        }
+        break;
+    case 4:
+        // "grad"
+        // "dpcm"
+        // "dppx"
+        // "vmin"
+        // "vmax"
+        // "turns"
+        // TODO(esprehn): Use the trie here too.
+        return unitTable().get(String(chars, length).lower());
+        break;
+    case 5:
+        // "__qem"

[Timothy Loh, 2016/04/27 06:52:05]

this isn't exposed, if it helps we can rename it to be shorter ;)

+        // TODO(esprehn): Use the trie here too.
+        return unitTable().get(String(chars, length).lower());
+        break;
+    }
+    return CSSPrimitiveValue::UnitType::Unknown;
+}
+
 } // namespace
 
 float CSSPrimitiveValue::clampToCSSLengthRange(double value)
@@ -102,7 +221,19 @@ void CSSPrimitiveValue::initUnitTable()
 
 CSSPrimitiveValue::UnitType CSSPrimitiveValue::fromName(const String& unit)
 {
-    return unitTable().get(unit.lower());
+    if (unit.is8Bit())
+        return toUnitType(unit.characters8(), unit.length());
+    return toUnitType(unit.characters16(), unit.length());
+}
+
+CSSPrimitiveValue::UnitType CSSPrimitiveValue::fromName(const LChar* characters8, unsigned length)
+{
+    return toUnitType(characters8, length);
+}
+
+CSSPrimitiveValue::UnitType CSSPrimitiveValue::fromName(const UChar* characters16, unsigned length)
+{
+    return toUnitType(characters16, length);
 }
 
 CSSPrimitiveValue::UnitCategory CSSPrimitiveValue::unitTypeToUnitCategory(UnitType type)